APL Nameplate
  • Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

Flickr Twitter iResearch App Facebook

BROWSE VOLUMES

Year Range: 
Search Issue | RSS Feeds RSS
Previous Issue Next Issue

13 Sep 2004

Volume 85, Issue 11, pp. 1871-2145

Issue Cover Spotlight Figure

Appl. Phys. Lett. 85, 1895 (2004); http://dx.doi.org/10.1063/1.1792802 (3 pages)

Markus Deubel, Martin Wegener, Artan Kaso, and Sajeev John
Enlarge Image | Read More
Page 2 of 4 Pages Previous Page Next Page | Jump to Page
back to top
RSS Feeds

Recombination dynamics of localized excitons in InGaN quantum dots

T. Bartel, M. Dworzak, M. Strassburg, A. Hoffmann, A. Strittmatter, and D. Bimberg

Appl. Phys. Lett. 85, 1946 (2004); http://dx.doi.org/10.1063/1.1790599 (3 pages) | Cited 28 times

Online Publication Date: 17 September 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Indium-rich fluctuations in ultrathin InGaN layers act at low temperatures as a dense ensemble of quantum dots (QD). This leads to a complex potential landscape with localization sites of widely varying depth for excitons. We report on investigations of the recombination mechanisms of excitons localized in InGaN∕GaN QD structures by time-resolved and spatially resolved photoluminescence (PL) measurements. The structures were grown by metal-organic chemical-vapor deposition on Si (111) substrates. Sharp lines originating from single QDs could be observed. Their PL decays show monoexponential behavior. Similar transition energies have different time constants. Thus, the well-known nonexponential PL decay of the QD ensemble is assigned to the summation of monoexponential decays originating from individual QDs with different exciton lifetimes.
Show PACS
73.21.La Quantum dots
78.67.Hc Quantum dots
78.47.-p Spectroscopy of solid state dynamics
68.65.Hb Quantum dots (patterned in quantum wells)
81.07.Ta Quantum dots
78.66.Fd III-V semiconductors
81.05.Ea III-V semiconductors
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
78.55.Cr III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Mechanical tuning of holographic polymer-dispersed liquid crystal reflection gratings

Scott A. Holmstrom, Lalgudi V. Natarajan, Vincent P. Tondiglia, Richard L. Sutherland, and Timothy J. Bunning

Appl. Phys. Lett. 85, 1949 (2004); http://dx.doi.org/10.1063/1.1790601 (3 pages) | Cited 11 times

Online Publication Date: 17 September 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Holographic polymer-dispersed liquid crystal reflective structures have been formed using a highly elastic photopolymer. The elasticity allows for mechanical tuning of the reflection notch by over 120 nm in the visible spectral range using compressive stress. The shift in the central position of the reflection notch is related to the strain in the system and an effective elastic modulus for the structure is obtained.
Show PACS
42.70.Df Liquid crystals
42.70.Jk Polymers and organics
42.40.Eq Holographic optical elements; holographic gratings
78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects
78.40.Me Organic compounds and polymers
62.10.+s Mechanical properties of liquids
61.30.Pq Microconfined liquid crystals: droplets, cylinders, randomly confined liquid crystals, polymer dispersed liquid crystals, and porous systems

Arrays of wirelike microstructures of Ag with visible wavelength transparent plasmonic response at near-ultraviolet and midinfrared regions

A. Biswas, R. Kunz, O. C. Aktas, M. Elbahri, R. Adelung, H. Takele, U. Saeed, U. Schürmann, V. Zaporojtchenko, and F. Faupel

Appl. Phys. Lett. 85, 1952 (2004); http://dx.doi.org/10.1063/1.1788895 (3 pages) | Cited 1 time

Online Publication Date: 17 September 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We present a simple masked thermal evaporation technique to fabricate arrays of wirelike Ag microstructures of width 8 μm with an extremely high aspect ratio on either silicon or glass substrates. In accordance with the theory of periodic arrays of thin wires, the electromagnetic response of Ag microstructures has shown a characteristic low-frequency plasmonic behavior with a transparent visible region. Plasmon absorption is observed to be splitted largely into transverse and predominating longitudinal bands at near-ultraviolet (415 nm) and midinfrared wavelengths (2867 nm), corresponding to the oscillation of the free electrons perpendicular to and along the long axis of the wires.
Show PACS
81.05.Bx Metals, semimetals, and alloys
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
78.40.Kc Metals, semimetals, and alloys
78.30.Er Solid metals and alloys
78.66.Bz Metals and metallic alloys

Hydrogen dilution profiling for hydrogenated microcrystalline silicon solar cells

Baojie Yan, Guozhen Yue, Jeffrey Yang, Subhendu Guha, D. L. Williamson, Daxing Han, and Chun-Sheng Jiang

Appl. Phys. Lett. 85, 1955 (2004); http://dx.doi.org/10.1063/1.1788877 (3 pages) | Cited 28 times

Online Publication Date: 17 September 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The structural properties of hydrogenated microcrystalline silicon solar cells are investigated using Raman, x-ray diffraction, and atomic force microscopy. The experimental results showed a significant increase of microcrystalline volume fraction and grain size with increasing film thickness. The correlation between the cell performance and the microstructure suggests that the increase of grain size and microcrystalline volume fraction with thickness is the main reason for the deterioration of cell performance as the intrinsic layer thickness increases. By varying the hydrogen dilution in the gas mixture during deposition, microstructure evolution has been controlled and cell performance significantly improved.
Show PACS
84.60.Jt Photoelectric conversion
78.66.Db Elemental semiconductors and insulators
81.05.Cy Elemental semiconductors
78.66.Jg Amorphous semiconductors; glasses
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
82.30.-b Specific chemical reactions; reaction mechanisms
52.77.Dq Plasma-based ion implantation and deposition
81.15.Jj Ion and electron beam-assisted deposition; ion plating
68.37.Ps Atomic force microscopy (AFM)

Effects of Ti–W codoping on the optical and electrical switching of vanadium dioxide thin films grown by a reactive pulsed laser deposition

M. Soltani, M. Chaker, E. Haddad, R. V. Kruzelecky, and J. Margot

Appl. Phys. Lett. 85, 1958 (2004); http://dx.doi.org/10.1063/1.1788883 (3 pages) | Cited 44 times

Online Publication Date: 17 September 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Thin films of thermochromic VO2, V1−xWxO2 and V1−x−yWxTiyO2 (x=0.014, and y=0.12) were synthesized onto quartz substrates using a reactive pulsed laser deposition technique. The films were then characterized by x-ray diffraction and x-ray photoelectron spectroscopy. The W and Ti dopant effects on the semiconductor-to-metal phase transition of VO2 were investigated by measuring the temperature dependence of their electrical resistivity and their infrared transmittance. Remarkably strong effects of Ti–W codoping were observed on both the optical and electrical properties of V1−x−yWxTiyO2 films. The IR transmittance was improved, while the transition temperature could be varied from 36°C for W-doped VO2 film to 60°C for Ti–W codoped VO2 film. In addition, at room temperature, a higher temperature coefficient of resistance of 5.12%∕°C is achieved. Finally, both optical and electrical hysteresis are completely suppressed by Ti–W codoping the VO2 films.
Show PACS
68.55.A- Nucleation and growth
78.20.N- Thermo-optic effects
78.20.nb Photothermal effects
71.30.+h Metal-insulator transitions and other electronic transitions
78.66.Nk Insulators
79.60.Bm Clean metal, semiconductor, and insulator surfaces
81.15.Fg Pulsed laser ablation deposition
78.30.Am Elemental semiconductors and insulators
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.S- Impurities in crystals

Compositional dependence of phase separation in InGaN layers

M. Rao, D. Kim, and S. Mahajan

Appl. Phys. Lett. 85, 1961 (2004); http://dx.doi.org/10.1063/1.1791327 (3 pages) | Cited 28 times

Online Publication Date: 17 September 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Phase separation in InGaN layers grown by metalorganic chemical vapor deposition on GaN epilayers was investigated using transmission electron microscopy. Layer thicknesses of 220 and 660 nm were deposited with InN fractions ranging from 3% to 34%. At InN contents of 3%, plan-view TEM images show a homogeneous microstructure and selected area diffraction (SAD) patterns exhibit no evidence of satellite spots. InN contents of 12% result in a speckled contrast. Satellites close to the fundamental spots belonging to the wurtzite structure are present in SAD patterns and they are indicative of composition modulations lying in the (0001) growth plane. No satellites are observed along the [0001] direction, implying that phase separation is two-dimensional in nature. Samples containing InN fractions of between 22% and 28% have microstructures exhibiting much stronger contrast variations. Satellite spots in SAD patterns are further spaced from the fundamental reflections. This trend continues on increasing InN content to 34%. In addition, cross-sectional TEM images show an absence of contrast from InGaN layers with InN contents above 12%, in the vicinity of the InGaN∕GaN interface, indicating that coherency strain inhibits phase separation. Arguments are developed to rationalize these observations.
Show PACS
81.05.Ea III-V semiconductors
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
64.75.-g Phase equilibria
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.37.Lp Transmission electron microscopy (TEM)

Structural and optical properties of Ba(Cox,Ti1−x)O3 thin films fabricated by sol-gel process

Y. W. Li, J. L. Sun, X. J. Meng, J. H. Chu, and W. F. Zhang

Appl. Phys. Lett. 85, 1964 (2004); http://dx.doi.org/10.1063/1.1786654 (3 pages) | Cited 6 times

Online Publication Date: 17 September 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Ba(Cox,Ti1−x)O3 thin films were prepared on fused quartz substrate by a sol-gel method. The results of x-ray diffraction showed that the films are perovskite phase and the change of lattice constant caused by different Co concentration is undetectable. Optical transmittance measurement indicated that Co doping has effect on the energy band structure. The energy gap of Ba(Cox,Ti1−x)O3 decreased linearly with the increase of Co concentration. It is inferred that the energy level of conduction bands decline with the Co content increasing. This result is similar to the phenomena found in binary semiconductor where the band gap decreases with the increasing of average atomic number.
Show PACS
77.55.-g Dielectric thin films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
78.66.Nk Insulators
81.10.Dn Growth from solutions
81.10.Fq Growth from melts; zone melting and refining
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
77.80.-e Ferroelectricity and antiferroelectricity
61.72.S- Impurities in crystals
68.55.-a Thin film structure and morphology
71.20.Ps Other inorganic compounds
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.30.Hv Other nonmetallic inorganics
68.55.A- Nucleation and growth

Structural evolution of dislocation half-loops in epitaxial BaTiO3 thin films during high-temperature annealing

H. P. Sun, X. Q. Pan, J. H. Haeni, and D. G. Schlom

Appl. Phys. Lett. 85, 1967 (2004); http://dx.doi.org/10.1063/1.1789233 (3 pages) | Cited 10 times

Online Publication Date: 17 September 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
BaTiO3 thin films were grown on (001) SrTiO3 by reactive molecular beam epitaxy. Transmission electron microscopy studies showed that there is a high density of dislocation half-loops inside 8- and 12-nm-thick films. By thermal annealing at 1000°C, the isolated small dislocation half-loops grow and combine to form a self-assembled regular dislocation network at the film/substrate interface. Threading dislocations in the films are removed and the lattice mismatch strain in the film is nearly completely relaxed by annealing at high temperature.
Show PACS
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
68.60.Bs Mechanical and acoustical properties
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.37.Lp Transmission electron microscopy (TEM)
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
81.40.Gh Other heat and thermomechanical treatments
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Crack-free and conductive Si-doped AlN∕GaN distributed Bragg reflectors grown on 6H-SiC(0001)

Tommy Ive, Oliver Brandt, Helmar Kostial, Thorsten Hesjedal, Manfred Ramsteiner, and Klaus H. Ploog

Appl. Phys. Lett. 85, 1970 (2004); http://dx.doi.org/10.1063/1.1791738 (3 pages) | Cited 22 times

Online Publication Date: 17 September 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We demonstrate Si-doped n-type AlN∕GaN distributed Bragg reflectors grown on 6H-SiC(0001). The structures are crack-free and have a stopband centered around 450 nm with a full width at half maximum between 40 and 50 nm. The maximum measured reflectance is ⩾99%. A comparison between Si-doped and undoped structures reveals no degradation of the reflectance due to the Si doping. Vertical conductance measurements at room temperature on the samples show an ohmic I–V behavior in the entire measurement range. The measured resistivity at 77 K is only a factor of 2 larger than the resistivity measured at room temperature.
Show PACS
81.05.Ea III-V semiconductors
42.79.Bh Lenses, prisms and mirrors
68.35.B- Structure of clean surfaces (and surface reconstruction)
61.72.S- Impurities in crystals
73.61.Ey III-V semiconductors
78.66.Fd III-V semiconductors
61.72.uj III-V and II-VI semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.30.Fs III-V and II-VI semiconductors

Lack of the critical pressure for weakening of size-induced stiffness in 3C–SiC nanocrystals under hydrostatic compression

Haozhe Liu, Jingzhu Hu, Jinfu Shu, Daniel Häusermann, and Ho-kwang Mao

Appl. Phys. Lett. 85, 1973 (2004); http://dx.doi.org/10.1063/1.1789240 (3 pages) | Cited 17 times

Online Publication Date: 17 September 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Using in situ high-pressure x-ray diffraction methods, the compressibility of 30 nm 3C–SiC nanocrystals was studied under hydrostatic conditions while helium was used as pressure transmitting medium, as well as under nonhydrostatic conditions without pressure medium. No threshold pressure phenomenon was observed for the compressibility of the nanocrystals during compression in hydrostatic conditions, while the critical pressure around 10.5 GPa was observed during nonhydrostatic compression. These indicate that the threshold pressure phenomena, recently reported that the nanocrystals initially exhibited much higher bulk modulus below the threshold pressure during compression [Appl. Phys. Lett. 83, 3174 (2003); J. Phys. Chem. 107, 14151 (2003)], were mainly caused by the nonhydrostatic effect instead of a specific feature of nanocrystals upon compression. The bulk modulus of 3C–SiC nanocrystals is estimated as 220.6±0.6 GPa based on the hydrostatic compression data.
Show PACS
62.50.-p High-pressure effects in solids and liquids
62.25.-g Mechanical properties of nanoscale systems
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity
81.40.Vw Pressure treatment

Direct evidence for selective impurity incorporation at the crystal domain boundaries in epitaxial ZnO layers

F. Bertram, D. Forster, J. Christen, N. Oleynik, A. Dadgar, and A. Krost

Appl. Phys. Lett. 85, 1976 (2004); http://dx.doi.org/10.1063/1.1791746 (3 pages) | Cited 6 times

Online Publication Date: 17 September 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A direct correlation of structural properties with the spatial distribution of bound exciton luminescence in ZnO epitaxial layers has been achieved on a microscopic scale using highly spatially and spectrally resolved cathodoluminescence. The morphology of the high quality ZnO layer is characterized by a distinct domain structure. While the laterally integrated cathodoluminescence spectrum shows narrow (full width at half maximum <3 meV) I8 luminescence, a pronounced emission line at I0∕I1 emerges in the local spectra taken at domain boundaries. In complete contrast, no I0∕I1 emission is found inside the domains. Monochromatic images further evidence the selective incorporation of impurities at the grain boundaries of domains. Micro mappings of the I8 peak wavelength directly visualize the strain relaxation across the domains toward their very center, where a drop in quantum efficiency indicates enhanced defect concentration.
Show PACS
81.05.Dz II-VI semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
71.55.Gs II-VI semiconductors
68.35.B- Structure of clean surfaces (and surface reconstruction)
61.72.S- Impurities in crystals
78.66.Hf II-VI semiconductors
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
78.60.Hk Cathodoluminescence, ionoluminescence
71.35.-y Excitons and related phenomena
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
68.60.Bs Mechanical and acoustical properties

Differential Hall effect profiling of ultrashallow junctions in Sb implanted silicon

T. Alzanki, R. Gwilliam, N. Emerson, and B. J. Sealy

Appl. Phys. Lett. 85, 1979 (2004); http://dx.doi.org/10.1063/1.1792378 (2 pages) | Cited 9 times

Online Publication Date: 17 September 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A differential Hall effect technique has been developed to obtain doping profiles at a depth resolution down to 2 nm with junction depths of about 20 nm. We have determined the electrical characteristics of 5×1014 Sb+ cm−2 implanted in (100) silicon at an energy of 5 keV. A comparison was made between carrier concentration profiles and secondary ion mass spectroscopy measurements of the atomic profiles as a function of annealing temperature. We have profiled single energy implants of antimony and also double implants; the latter enables complete profiles to be measured down to the background level of about 1018 cm−3.
Show PACS
61.72.uf Ge and Si
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.61.Cw Elemental semiconductors
72.20.My Galvanomagnetic and other magnetotransport effects
81.05.Cy Elemental semiconductors
61.72.S- Impurities in crystals
61.80.Jh Ion radiation effects
81.40.Gh Other heat and thermomechanical treatments

Critical effects of substrate terraces and steps morphology on the growth mode of epitaxial SrRuO3 films

F. Sánchez, G. Herranz, I. C. Infante, J. Fontcuberta, M. V. García-Cuenca, C. Ferrater, and M. Varela

Appl. Phys. Lett. 85, 1981 (2004); http://dx.doi.org/10.1063/1.1786361 (3 pages) | Cited 20 times

Online Publication Date: 17 September 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We report on the controlled fabrication of the arrays of self-organized fingerlike nanostructures of SrRuO3 that form on SrTiO3(001). We show that the size (width and height) of the one-dimensional nanometric units can be tuned or suppressed by using appropriate substrate vicinality θv and surface termination. Critical effects on the fingers height are observed when θv is below an angle as small as ∼0.1°. The value of θv also determines if the final two-dimensional growth is by a step flow (θv=0.5°), by layer by layer (θv=0.04°), or by coexistence of both mechanisms (θv=0.1°). The fingers are suppressed when TiO2-terminated low-miscut substrates are used, as film nucleation takes place on the terraces and then substrate steps are not active as templates for the one-dimensional structure formation. These findings shall contribute to progress toward lateral nanostructuration of complex oxide surfaces.
Show PACS
81.07.Bc Nanocrystalline materials
61.46.-w Structure of nanoscale materials
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
81.15.Fg Pulsed laser ablation deposition
81.16.Dn Self-assembly
back to top
RSS Feeds

Minority carrier diffusion length and lifetime for electrons in a type-II InAs∕GaSb superlattice photodiode

Jian V. Li, Shun Lien Chuang, Eric M. Jackson, and Edward Aifer

Appl. Phys. Lett. 85, 1984 (2004); http://dx.doi.org/10.1063/1.1787598 (3 pages) | Cited 8 times

Online Publication Date: 17 September 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We use the electron-beam-induced current (EBIC) technique to investigate carrier transport characteristics in a type-II InAs∕GaSb superlattice photodiode with cutoff wavelength at 7.7 μm. We use a theoretical model that includes an extended generation source and depletion region to simulate the EBIC current on both sides of the p–n junction. The electron minority diffusion length in the p-superlattice, Le, is extracted from the simulation, from which the electron lifetime τe is obtained. Le increases from 0.275 μm at 5.3 K to 0.355 μm at 100 K. τe drops from 1.5 ns at 5.3 K to 0.13 ns at 100 K.
Show PACS
85.30.De Semiconductor-device characterization, design, and modeling
85.60.Dw Photodiodes; phototransistors; photoresistors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)

Variable range hopping in a C60 field-effect transistor

Kazunaga Horiuchi, Shin Uchino, Shinobu Hashii, Akira Hashimoto, Tomohiro Kato, Takahiko Sasaki, Nobuyuki Aoki, and Yuichi Ochiai

Appl. Phys. Lett. 85, 1987 (2004); http://dx.doi.org/10.1063/1.1790036 (3 pages) | Cited 6 times

Online Publication Date: 17 September 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A variable range hopping (VRH) has been observed in the low-temperature conductance of a C60 field-effect transistor. We have investigated a thermal annealing (TA) effect at 453 and 498 K, on the conductance in various gate voltages and several source-drain separations. VRH analysis shows that density of states in the pseudogap clearly decreases as TA temperature increases. However, there might exist the other charge trapping states at interfaces with electrodes and gate dielectric, which could be modulated also by TA.
Show PACS
85.30.Tv Field effect devices
73.50.Dn Low-field transport and mobility; piezoresistance
73.61.Wp Fullerenes and related materials
73.20.At Surface states, band structure, electron density of states

Ballistic electron emission luminescence spectroscopy of an InAs quantum dot heterostructure

Wei Yi, Ian Appelbaum, K. J. Russell, V. Narayanamurti, M. P. Hanson, and A. C. Gossard

Appl. Phys. Lett. 85, 1990 (2004); http://dx.doi.org/10.1063/1.1790595 (3 pages) | Cited 7 times

Online Publication Date: 17 September 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We present ballistic electron emission luminescence (BEEL) spectroscopy measurements of an InAs quantum dot (QD) heterostructure based on three-terminal hot electron injection using a scanning tunneling microscope (STM) and a planar tunnel-junction transistor. Due to higher injected current, the planar transistors allow us to perform wavelength spectroscopy of the emitted luminescence, which resolves both quantum-confined Stark-shifted QD luminescence near 1.34 eV and bulk GaAs luminescence at 1.48 eV. This facilitates interpretation of STM BEEL spectra as a function of collector voltage bias. By freezing out the collector leakage current at low temperatures, consistent collector-current spectra are acquired with both STM and planar transistors.
Show PACS
73.63.Kv Quantum dots
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
78.67.Hc Quantum dots
78.60.Fi Electroluminescence
68.37.Vj Field emission and field-ion microscopy
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
73.23.Ad Ballistic transport
79.70.+q Field emission, ionization, evaporation, and desorption

Carrier transport in transparent oxide semiconductor with intrinsic structural randomness probed using single-crystalline InGaO3(ZnO)5 films

Kenji Nomura, Toshio Kamiya, Hiromichi Ohta, Kazushige Ueda, Masahiro Hirano, and Hideo Hosono

Appl. Phys. Lett. 85, 1993 (2004); http://dx.doi.org/10.1063/1.1788897 (3 pages) | Cited 68 times

Online Publication Date: 17 September 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We have investigated carrier transport in a crystalline oxide semiconductor InGaO3(ZnO)5 using single-crystalline thin films. When carrier concentration is less than 2×1018 cm−3, logarithm of electrical conductivity decreases in proportion to T −1∕4 and room-temperature Hall mobility was as low as ∼1 cm2(V s)−1. When carrier concentration was increased to 4×1018 cm−3, the conduction mechanism changed to degenerate conduction and room-temperature Hall mobility was steeply increased to >10 cm2(Vs)−1, showing metal–insulator transition behavior. These results are explained by percolation conduction over distribution of potential barriers formed around conduction band edge. The potential distribution is a consequence of potential modulation originating from random distribution of Ga3+ and Zn2+ ions in the crystal structure of InGaO3(ZnO)5.
Show PACS
73.61.Le Other inorganic semiconductors
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
72.20.Ee Mobility edges; hopping transport
72.20.My Galvanomagnetic and other magnetotransport effects
68.55.-a Thin film structure and morphology
71.30.+h Metal-insulator transitions and other electronic transitions
71.20.Nr Semiconductor compounds
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Tunnel magnetoresistance in GaMnAs: Going beyond Jullière formula

L. Brey, C. Tejedor, and J. Fernández-Rossier

Appl. Phys. Lett. 85, 1996 (2004); http://dx.doi.org/10.1063/1.1789241 (3 pages) | Cited 35 times

Online Publication Date: 17 September 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The relation between tunnel magnetoresistance (TMR) and spin polarization is explored for GaMnAs∕GaAlAs∕GaMnAs structures where the carriers experience strong spin–orbit interactions. TMR is calculated using the Landauer approach. The materials are described in the 6 band k⋅p model which includes spin–orbit interaction. Ferromagnetism is described in the virtual crystal mean field approximations. Our results indicate that TMR is a function of spin polarization and barrier thickness. As a result of the stong spin–orbit interactions, TMR also depends on the the angle between current flow direction and the electrode magnetization. These results compromise the validity of Julliere formula.
Show PACS
75.50.Pp Magnetic semiconductors
75.50.Dd Nonmetallic ferromagnetic materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.47.Pq Other materials
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
72.20.My Galvanomagnetic and other magnetotransport effects
71.15.-m Methods of electronic structure calculations

Visualization of buried SiGe quantum dots at cleavages by cross-sectional atomic force microscopy

M. S. Dunaevskii, A. N. Titkov, Z. F. Krasilnik, A. V. Novikov, D. N. Lobanov, and R. Laiho

Appl. Phys. Lett. 85, 1999 (2004); http://dx.doi.org/10.1063/1.1791744 (3 pages)

Online Publication Date: 17 September 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Cross-sectional atomic force microscopy (XAFM) is used to visualize in ambient atmosphere SiGe quantum dots (QDs) embedded in Si. Buried QDs are revealed as nanometer high topographic features on cross-sectional cleavages of the samples. Details of the images are used to get information about strain relaxation of the QDs and its relationship with the shape of the surface relief. We propose XAFM as a simple method to check the presence of QDs and to estimate their sizes and surface density. This method also allows detailed investigation of effects related to vertical alignment of the dots in different layers of multilayer QD structures.
Show PACS
68.65.Hb Quantum dots (patterned in quantum wells)
68.35.B- Structure of clean surfaces (and surface reconstruction)
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
68.37.Ps Atomic force microscopy (AFM)

Electrical transport properties of single ZnO nanorods

Y. W. Heo, L. C. Tien, D. P. Norton, B. S. Kang, F. Ren, B. P. Gila, and S. J. Pearton

Appl. Phys. Lett. 85, 2002 (2004); http://dx.doi.org/10.1063/1.1792373 (3 pages) | Cited 80 times

Online Publication Date: 17 September 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Single ZnO nanorods with diameters of ∼130 nm were grown on Au-coated Al2O3 substrates by catalyst-driven molecular beam epitaxy. Individual nanorods were removed from the substrate and placed between Ohmic contact pads and the current–voltage characteristics measured as a function of temperature and gas ambient. In the temperature range from 25 to 150 °C, the resistivity of nanorods treated in H2 at 400 °C prior to measurement showed an activation energy of 0.089±0.02 eV and was insensitive to the ambient used (C2H4,N2O,O2 or 10% H2 in N2). By sharp contrast, the conductivity of nanorods not treated in H2 was sensitive to trace concentrations of gases in the measurement ambient even at room temperature, demonstrating their potential as gas sensors.
Show PACS
81.05.Dz II-VI semiconductors
81.07.Bc Nanocrystalline materials
73.40.Ns Metal-nonmetal contacts
73.63.Bd Nanocrystalline materials
61.46.-w Structure of nanoscale materials
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing

Time-resolved detection of individual electrons in a quantum dot

R. Schleser, E. Ruh, T. Ihn, K. Ensslin, D. C. Driscoll, and A. C. Gossard

Appl. Phys. Lett. 85, 2005 (2004); http://dx.doi.org/10.1063/1.1784875 (3 pages) | Cited 15 times

Online Publication Date: 17 September 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We present measurements on a quantum dot and a nearby, capacitively coupled, quantum point contact used as a charge detector. With the dot being weakly coupled to only a single reservoir, the transfer of individual electrons onto and off the dot can be observed in real time in the current signal from the quantum point contact. From these time-dependent traces, the quantum mechanical coupling between dot and reservoir can be extracted quantitatively. A similar analysis allows the determination of the occupation probability of the dot states.
Show PACS
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
68.37.Ps Atomic force microscopy (AFM)
73.61.Ey III-V semiconductors

Confinement in silicon nanowires: Optical properties

S. Bhattacharya, D. Banerjee, K. W. Adu, S. Samui, and Somnath Bhattacharyya

Appl. Phys. Lett. 85, 2008 (2004); http://dx.doi.org/10.1063/1.1787164 (3 pages) | Cited 16 times

Online Publication Date: 17 September 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The blueshift of the optical absorption edge along with the intense red photoluminescence (PL) peak has been observed from micron-long crystalline silicon nanowires prepared by pulsed-laser vaporization of heated Si (mixed with metal catalyst) targets. Previous studies on the confinement in silicon nanostructures resulted in a dispute regarding the application of theoretical models to explain their optical properties. Based on the microstructure a phenomenological confinement model, incorporating the nanowire diameter distribution is used, which is found to describe the optical properties including the shape of absorption spectra, the band gap, and the PL peak position of the Si nanowires very well.
Show PACS
81.07.Bc Nanocrystalline materials
81.05.Cy Elemental semiconductors
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
78.55.Ap Elemental semiconductors
61.46.-w Structure of nanoscale materials
81.16.Mk Laser-assisted deposition
81.15.Fg Pulsed laser ablation deposition
back to top
RSS Feeds

Magnetic properties and band structures of half-metal-type Co2CrGa Heusler alloy

R. Y. Umetsu, K. Kobayashi, R. Kainuma, A. Fujita, K. Fukamichi, K. Ishida, and A. Sakuma

Appl. Phys. Lett. 85, 2011 (2004); http://dx.doi.org/10.1063/1.1790029 (3 pages) | Cited 30 times

Online Publication Date: 17 September 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The saturation magnetic moment Ms and the Curie temperature TC of the half-metal-type Co2CrGa Heusler alloy have been investigated. The value of Ms at 4.2 K for the L21-type Co2CrGa alloy is 3.01 μB∕f.u., in agreement with the generalized Slater-Pauling line and the theoretical calculation. The Curie temperature TC and the phase-transformation temperature Tt from the L21 to B2-type structure are 495 and 1050 K, respectively. The band calculations disclose that the spin polarization is also relatively high in the B2-type structure, although its estimated TC is about 100 K lower than that of the L21-type structure.
Show PACS
75.50.Cc Other ferromagnetic metals and alloys
75.30.Cr Saturation moments and magnetic susceptibilities
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
71.20.Be Transition metals and alloys
72.25.Ba Spin polarized transport in metals
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Electronic structure and spin polarization of MnGaP

Leeor Kronik, Manish Jain, and James R. Chelikowsky

Appl. Phys. Lett. 85, 2014 (2004); http://dx.doi.org/10.1063/1.1787895 (3 pages) | Cited 4 times

Online Publication Date: 17 September 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We present ab initio pseudopotential–density-functional calculations for the electronic structure of the dilute magnetic semiconductor MnxGa1−xP, with a realistic x=0.063, in its ordered ferromagnetic phase. We find that it possesses a spin-polarized valence band that could support ideal spin-polarized hole transport. We further find spin-polarized features in the conduction band that could support ideal spin-polarized transport of minority electrons. As such, it emerges as a silicon-lattice-matched candidate material for spintronics applications.
Show PACS
75.50.Pp Magnetic semiconductors
75.50.Dd Nonmetallic ferromagnetic materials
71.20.Nr Semiconductor compounds
72.25.Dc Spin polarized transport in semiconductors
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
71.15.Dx Computational methodology (Brillouin zone sampling, iterative diagonalization, pseudopotential construction)

Properties of MgB2 thin films with carbon doping

A. V. Pogrebnyakov, X. X. Xi, J. M. Redwing, V. Vaithyanathan, D. G. Schlom, A. Soukiassian, S. B. Mi, C. L. Jia, J. E. Giencke, C. B. Eom, J. Chen, Y. F. Hu, Y. Cui, and Qi Li

Appl. Phys. Lett. 85, 2017 (2004); http://dx.doi.org/10.1063/1.1782258 (3 pages) | Cited 49 times

Online Publication Date: 17 September 2004

Full Text: Read Online (HTML) | Download PDF


See Also: Erratum

Show Abstract
We have studied structural and superconducting properties of MgB2 thin films doped with carbon during the hybrid physical-chemical vapor deposition process. A carbon-containing precursor metalorganic bis(methylcyclopentadienyl)magnesium was added to the carrier gas to achieve carbon doping. As the amount of carbon in the film increases, the resistivity increases, Tc decreases, and the upper critical field increases dramatically as compared to clean films. The self-field Jc in the carbon doped film is lower than that in the clean film, but Jc remains relatively high to much higher magnetic fields, indicating stronger pinning. Structurally, the doped films are textured with columnar nano-grains and highly resistive amorphous areas at the grain boundaries. The carbon doping approach can be used to produce MgB2 materials for high magnetic-field applications.
Show PACS
74.70.Ad Metals; alloys and binary compounds (including A15, MgB2, etc.)
74.78.-w Superconducting films and low-dimensional structures
74.25.F- Transport properties
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
74.25.Sv Critical currents
68.55.-a Thin film structure and morphology
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Mm Grain and twin boundaries
61.72.S- Impurities in crystals
Page 2 of 4 Pages Previous Page Next Page | Jump to Page
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close