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27 Jan 2003

Volume 82, Issue 4, pp. 487-659

Issue Cover Spotlight Figure

Appl. Phys. Lett. 82, 559 (2003); http://dx.doi.org/10.1063/1.1539543 (3 pages)

P. R. C. Kent and Alex Zunger
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Structural reconstruction of hexagonal to cubic ZnO films on Pt/Ti/SiO2/Si substrate by annealing

Sung-Kyu Kim, Se-Young Jeong, and Chae-Ryong Cho

Appl. Phys. Lett. 82, 562 (2003); http://dx.doi.org/10.1063/1.1536253 (3 pages) | Cited 29 times

Online Publication Date: 22 January 2003

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It is well known that ZnO generally has the wurtzite structure. We report the growth of both hexagonal and cubic ZnO on Pt(111)/Ti/SiO2/Si substrate by a solution deposition. The wurtzite structure of ZnO film is enhanced up to the annealing temperature of 600 °C, and disappeared for annealing temperatures above 700 °C. The Pt(111)/Ti/SiO2/Si substrate is reoriented to hexagonal-Pt3Ti(004)/Ti/SiO2/Si when annealed at 700 °C and above due to the Ti out-diffusion and the ZnO thin film grown on the substrate has a cubic structure. The diffusion of Ti was evidenced by Auger electron spectroscopy measurements. From the photoluminescence measurement, the band gap of the wurtzite structure of ZnO film grown by the annealing below 600 °C was 3.37 eV, as is already known, but the cubic ZnO had a band gap of 3.28 eV, which suggests a zinc blende structure. The stability of the zinc blende structure on Zn2TiO4 layer was checked by the calculation of the lattice mismatch using the extended atomic distance mismatch model. Additionally the formation of the zinc blende ZnO could be prevented by using the Pt(111)/TiO2/SiO2/Si substrate. © 2003 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.05.Dz II-VI semiconductors
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
64.70.K- Solid-solid transitions
78.55.Et II-VI semiconductors
78.66.Hf II-VI semiconductors
61.72.Cc Kinetics of defect formation and annealing
79.20.Fv Electron impact: Auger emission
68.60.Dv Thermal stability; thermal effects
71.20.Nr Semiconductor compounds
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Photoconductivity and spin-dependent photoconductivity of hydrosilylated (111) silicon surfaces

A. Lehner, F. Kohl, S. A. Franzke, T. Graf, M. S. Brandt, and M. Stutzmann

Appl. Phys. Lett. 82, 565 (2003); http://dx.doi.org/10.1063/1.1540732 (3 pages) | Cited 10 times

Online Publication Date: 22 January 2003

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Organic monolayers were prepared on hydrogen-terminated (111) silicon surfaces by thermally induced hydrosilylation with alkenes. The electronic properties of the modified surfaces were studied by photoconductivity and spin-dependent photoconductivity measurements (electrically detected magnetic resonance) and compared to the oxidized and hydrogen-terminated silicon surfaces. The photoconductivity at low intensity of illumination (monomolecular recombination regime) indicates that the hydrosilylated surface has nearly as few defects as the surfaces treated in HF vapor. The paramagnetic defects detected in the spin-dependent photoconductivity are identified as the silicon dangling bond Pb-center. The density of defects at the hydrosilylated (111) silicon surface is determined by electron spin resonance measurements to be about 1013 cm−2. © 2003 American Institute of Physics.
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72.40.+w Photoconduction and photovoltaic effects
73.20.Hb Impurity and defect levels; energy states of adsorbed species
76.30.Mi Color centers and other defects
81.05.Cy Elemental semiconductors
81.65.Rv Passivation
71.55.Cn Elemental semiconductors

Mechanisms responsible for improvement of 4H–SiC/SiO2 interface properties by nitridation

V. V. Afanas’ev, A. Stesmans, F. Ciobanu, G. Pensl, K. Y. Cheong, and S. Dimitrijev

Appl. Phys. Lett. 82, 568 (2003); http://dx.doi.org/10.1063/1.1532103 (3 pages) | Cited 53 times

Online Publication Date: 22 January 2003

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An analysis of fast and slow traps at the interface of 4H–SiC with oxides grown in O2, N2O, and NO reveals that the dominant positive effect of nitridation is due to a significant reduction of the slow electron trap density. These traps are likely to be related to defects located in the near-interfacial oxide layer. In addition, the analysis confirms that the fast interface states related to clustered carbon are also reduced by nitridation. © 2003 American Institute of Physics.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.20.Hb Impurity and defect levels; energy states of adsorbed species
68.35.Dv Composition, segregation; defects and impurities
81.65.Rv Passivation

CdS and Cd(OH)2 formation during Cd treatments of Cu(In,Ga)(S,Se)2 thin-film solar cell absorbers

L. Weinhardt, Th. Gleim, O. Fuchs, C. Heske, E. Umbach, M. Bär, H.-J. Muffler, Ch.-H. Fischer, M. C. Lux-Steiner, Y. Zubavichus, T. P. Niesen, and F. Karg

Appl. Phys. Lett. 82, 571 (2003); http://dx.doi.org/10.1063/1.1539553 (3 pages) | Cited 32 times

Online Publication Date: 22 January 2003

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The surface modifications induced by treating Cu(In,Ga)(S,Se)2 films in an aqueous ammonia hydroxide-based solution of Cd2+ ions—as used in record Cu(In,Ga)(S,Se)2 solar cells without a CdS buffer layer—have been investigated for different Cd2+ concentrations. Employing a combination of x-ray photoelectron spectroscopy, Auger electron spectroscopy, and x-ray emission spectroscopy, it is possible to distinguish two different surface modifications. For Cd2+ concentrations below 4.5 mM in the solution we observe the formation of a CdS monolayer, while higher Cd2+ concentrations lead to the additional deposition of a cadmium hydroxide film on the CdS/Cu(In,Ga)(S,Se)2 surface. © 2003 American Institute of Physics.
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81.65.-b Surface treatments
81.05.Hd Other semiconductors
42.79.Ek Solar collectors and concentrators
84.60.Jt Photoelectric conversion
79.60.Dp Adsorbed layers and thin films
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
78.70.En X-ray emission spectra and fluorescence

Electronic and transport properties of reduced and oxidized nanocrystalline TiO2 films

A. Rothschild, Y. Komem, A. Levakov, N. Ashkenasy, and Yoram Shapira

Appl. Phys. Lett. 82, 574 (2003); http://dx.doi.org/10.1063/1.1539556 (3 pages) | Cited 29 times

Online Publication Date: 22 January 2003

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Electronic properties of reduced (vacuum-annealed) and oxidized (air-annealed) TiO2 films were investigated by in situ conductivity and current–voltage measurements as a function of the ambient oxygen pressure and temperature, and by ex situ surface photovoltage spectroscopy. The films were quite conductive in the reduced state but their resistance drastically increased upon exposure to air at 350 °C. In addition, the surface potential barrier was found to be much larger for the oxidized versus the reduced films. This behavior may be attributed to the formation of surface and grain boundary barriers due to electron trapping at interface states associated with chemisorbed oxygen species. © 2003 American Institute of Physics.
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73.61.Le Other inorganic semiconductors
73.63.Bd Nanocrystalline materials
73.50.Pz Photoconduction and photovoltaic effects
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
81.15.Cd Deposition by sputtering
81.07.Bc Nanocrystalline materials
61.72.Cc Kinetics of defect formation and annealing
73.25.+i Surface conductivity and carrier phenomena
73.20.Hb Impurity and defect levels; energy states of adsorbed species

Correlated charge detection for readout of a solid-state quantum computer

T. M. Buehler, D. J. Reilly, R. Brenner, A. R. Hamilton, A. S. Dzurak, and R. G. Clark

Appl. Phys. Lett. 82, 577 (2003); http://dx.doi.org/10.1063/1.1539904 (3 pages) | Cited 24 times

Online Publication Date: 22 January 2003

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The single-electron transistor (SET) is a prime candidate for reading out the final state of a qubit in a solid-state quantum computer. Such a measurement requires the detection of subelectron charge motion in the presence of random charging events. We present a detection scheme where the signals from two SETs are cross-correlated to suppress unwanted artifacts due to charge noise. This technique is demonstrated by using the two SETs to detect the charge state of two coupled metal dots, thereby simulating charge transfer and readout in a two-qubit system. These measurements indicate that for comparable buried dopant semiconductor architectures, the minimum measurement time required to distinguish between the two charge states is of the order of 10 ns. © 2003 American Institute of Physics.
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03.67.Lx Quantum computation architectures and implementations
85.35.Gv Single electron devices
73.21.La Quantum dots

Electrical properties of metal contacts on laser-irradiated n-type GaN

Ho Won Jang, Jong Kyu Kim, Jong-Lam Lee, J. Schroeder, and T. Sands

Appl. Phys. Lett. 82, 580 (2003); http://dx.doi.org/10.1063/1.1537515 (3 pages) | Cited 12 times

Online Publication Date: 22 January 2003

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The electrical properties of metal contacts on laser-irradiated n-type GaN were investigated using synchrotron radiation photoemission spectroscopy. A KrF excimer laser pulse of 600 mJ/cm2 onto GaN led to a decrease in the Ni Schottky barrier height from 0.91 to 0.47 eV, resulting in the formation of a nonalloyed Ohmic contact with a specific contact resistivity of 1.7×10−6 Ω cm2. Metallic Ga decomposed from GaN by laser irradiation was transformed into GaOx, playing a role in promoting outdiffusion of N atoms. A large number of N vacancies were produced, forming a degenerated GaN layer near the surface, resulting in the good Ohmic contact. © 2003 American Institute of Physics.
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73.40.Ns Metal-nonmetal contacts
61.82.Fk Semiconductors
79.60.Jv Interfaces; heterostructures; nanostructures
73.40.Cg Contact resistance, contact potential
79.20.Ds Laser-beam impact phenomena
68.35.Fx Diffusion; interface formation
61.72.J- Point defects and defect clusters
68.37.Ps Atomic force microscopy (AFM)

Effect of microstructural change on magnetic property of Mn-implanted p-type GaN

Jeong Min Baik, Ho Won Jang, Jong Kyu Kim, and Jong-Lam Lee

Appl. Phys. Lett. 82, 583 (2003); http://dx.doi.org/10.1063/1.1541111 (3 pages) | Cited 35 times

Online Publication Date: 22 January 2003

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A dilute magnetic semiconductor was achieved by implanting Mn ions into p-type GaN and subsequent annealing. The ferromagnetic property was obtained after annealing at 800 °C. This was attributed to the formation of Ga–Mn magnetic phases. Higher temperature annealing at 900 °C reduced the ferromagnetic signal and produced antiferromagnetic Mn–N compounds such as Mn6N2.58 and Mn3N2, leaving N vacancies. This provides evidence that N vacancies play a critical role in weakening the ferromagnetic property in the Mn-implanted GaN. © 2003 American Institute of Physics.
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81.40.Rs Electrical and magnetic properties related to treatment conditions
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.50.Pp Magnetic semiconductors
81.40.Gh Other heat and thermomechanical treatments
75.50.Dd Nonmetallic ferromagnetic materials
75.50.Ee Antiferromagnetics
61.72.J- Point defects and defect clusters

Neutron radiation effects on the nonlinear current–voltage characteristics of ilmenite-hematite ceramics

P. Padmini, M. Pulikkathara, R. Wilkins, and R. K. Pandey

Appl. Phys. Lett. 82, 586 (2003); http://dx.doi.org/10.1063/1.1537030 (3 pages) | Cited 4 times

Online Publication Date: 22 January 2003

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Ilmenite-hematite (IH) is a wide-band gap semiconducting material with a potential for low-voltage varistor applications. The nonlinear characteristics of this material were investigated before and after exposure to high-energy neutron radiation. The typical current–voltage characteristics of a varistor device are retained in all our samples subjected to neutron radiation. However, the effect is more pronounced on the device parameters like the nonlinear coefficient (α) and switching field (Es). The crystallinity of the ceramic remains unaffected after irradiation. Our observations confirm that IH-based varistor devices can perform satisfactorily even in radiation dominant environments such as in space and nuclear reactors. © 2003 American Institute of Physics.
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72.20.Ht High-field and nonlinear effects
72.80.Jc Other crystalline inorganic semiconductors
61.80.Hg Neutron radiation effects
61.82.Fk Semiconductors

Strain-induced growth of SiO2 dots by liquid phase deposition

C. W. Liu, B.-C. Hsu, K.-F. Chen, M. H. Lee, C.-R. Shie, and Pang-Shiu Chen

Appl. Phys. Lett. 82, 589 (2003); http://dx.doi.org/10.1063/1.1542682 (3 pages) | Cited 1 time

Online Publication Date: 22 January 2003

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Silicon dioxide dots are deposited on the Si cap layers of self-assembled Ge dots using a liquid phase deposition method. The Si capping layer directly above the Ge dots has a tensile strain, while the Si cap on the wetting layer is not strained. The tensile strain can enhance the silicon dioxide nucleation and deposition on Si surface, and SiO2 dots are directly formed on the top of Ge dots with the SiO2 wetting layers between the dots. The step height and base width of the dots increase with the deposition time. A metal-oxide-semiconductor photodetector is fabricated using the liquid-phase-deposited oxide, and has a responsivity of 0.08 mA/W at 1550 nm. © 2003 American Institute of Physics.
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81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
68.55.A- Nucleation and growth
68.65.Hb Quantum dots (patterned in quantum wells)

Shallow donor state of hydrogen in indium nitride

E. A. Davis, S. F. J. Cox, R. L. Lichti, and C. G. Van de Walle

Appl. Phys. Lett. 82, 592 (2003); http://dx.doi.org/10.1063/1.1539547 (3 pages) | Cited 45 times

Online Publication Date: 22 January 2003

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The nature of the electron states associated with hydrogen in InN has been inferred by studying the behavior of positive muons, which mimic protons when implanted into semiconductors. The muons capture electrons below 60 K, forming paramagnetic centers with a binding energy of about 12 meV. Together with an exceedingly small muon-electron hyperfine constant indicative of a highly delocalized electron wave function, the results confirm the recently predicted shallow-donor properties of hydrogen in InN. © 2003 American Institute of Physics.
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71.55.Eq III-V semiconductors
81.05.Ea III-V semiconductors
76.75.+i Muon spin rotation and relaxation
71.70.Jp Nuclear states and interactions

Structural and electrical properties of an electron-beam-irradiated C60 film

Jun Onoe, Tomonobu Nakayama, Masakazu Aono, and Toshiki Hara

Appl. Phys. Lett. 82, 595 (2003); http://dx.doi.org/10.1063/1.1542943 (3 pages) | Cited 61 times

Online Publication Date: 22 January 2003

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The structural and electrical properties of an electron-beam (EB)-irradiated C60 film have been examined at room temperature, using in situ infrared (IR) spectroscopy and ex situ four-probe measurements. IR results show that the irradiated film is neither graphite nor carbon nanotube-like but a peanut-shaped C60 polymer. Current–voltage curve shows that the polymer exhibits a metallic property with a drastically reduced resistivity of 7 Ω cm in comparison with 108–1014 Ω cm for solid C60. This indicates the possibility of applying C60 molecules in EB nanofabrication processes and large potential for developing carbon-based nanodevices. © 2003 American Institute of Physics.
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61.48.-c Structure of fullerenes and related hollow and planar molecular structures
73.61.Wp Fullerenes and related materials
78.30.Na Fullerenes and related materials
78.66.Tr Fullerenes and related materials
72.80.Rj Fullerenes and related materials
81.05.ub Fullerenes and related materials
68.55.-a Thin film structure and morphology
61.80.Fe Electron and positron radiation effects

Determination of the in-plane anisotropy of the electron effective mass tensor in 6H–SiC

H. P. Iwata

Appl. Phys. Lett. 82, 598 (2003); http://dx.doi.org/10.1063/1.1539545 (3 pages) | Cited 5 times

Online Publication Date: 22 January 2003

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An experimental evidence for the strong in-plane anisotropy of the electron effective mass tensor in 6H–SiC is reported. Furthermore, two components of the mass tensor in 6H–SiC, mM−Γ∗ and mM−K∗, have been resolved by making a theoretical bridge between Hall effect measurements and cyclotron resonance experiments, based on the Boltzmann transport equation. The method to resolve the in-plane effective mass components is also applied for 4H–SiC, which have already been resolved by cyclotron resonance. The values determined by our method are fully consistent with available experiments and calculations. © 2003 American Institute of Physics.
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71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
81.05.Hd Other semiconductors
71.20.Nr Semiconductor compounds
72.20.My Galvanomagnetic and other magnetotransport effects
76.40.+b Diamagnetic and cyclotron resonances
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Noncontacting measurement of the inductive nonlinearity of a superconducting thin film

J. H. Claassen

Appl. Phys. Lett. 82, 601 (2003); http://dx.doi.org/10.1063/1.1539554 (3 pages) | Cited 3 times

Online Publication Date: 22 January 2003

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Superconducting films are expected to contribute nonlinear effects in microwave circuits due to a current dependence of penetration depth λ. Data from a two-coil mutual inductance measurement can be used to extract the coefficient J0 representing a dependence of the form λ2(J) = λ2(0)[1+(J/J0)2]. A method of extracting J0, using a measurement of third-harmonic generation, is compared to one previously reported. The method is significantly easier to use and probably more accurate. Measurements on a number of YBa2Cu3O7−x films at 78 K have shown no sign of a nonquadratic nonlinearity, and give values of J0 as high as ∼100 MA/cm2.
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74.78.-w Superconducting films and low-dimensional structures
74.72.-h Cuprate superconductors
74.25.Ha Magnetic properties including vortex structures and related phenomena
84.40.-x Radiowave and microwave (including millimeter wave) technology

Single domain observation for synthetic antiferromagnetically coupled bits with low aspect ratios

N. Tezuka, N. Koike, K. Inomata, and S. Sugimoto

Appl. Phys. Lett. 82, 604 (2003); http://dx.doi.org/10.1063/1.1539549 (3 pages) | Cited 12 times

Online Publication Date: 22 January 2003

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Arrays of the synthetic antiferromagnetic (SyAF) patterned bits were successfully fabricated with micron to submicron sizes. Magnetic domain structure was investigated using magnetic force microscopy (MFM) for the SyAF bits as well as monolayer bits. MFM image of Co90Fe10(10 nm)/Ru(0.6 nm)/Co90Fe10(6 nm) SyAF bits demonstrates single domain structure for even a small aspect ratio of 1, while the 10 nm Co90Fe10 monolayer bits showed multi-domain structure for the aspect ratios below 2. This result indicates the predominance of the SyAF for ultrahigh bit density magnetic random access memory devices, because the bits with aspect ratio of 1 possessing single domain structure can provide size-independent switching field. © 2003 American Institute of Physics.
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75.70.Kw Domain structure (including magnetic bubbles and vortices)
85.75.Dd Magnetic memory using magnetic tunnel junctions
81.07.-b Nanoscale materials and structures: fabrication and characterization
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.50.Ee Antiferromagnetics
75.50.Bb Fe and its alloys
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
85.75.Bb Magnetic memory using giant magnetoresistance
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
72.15.Gd Galvanomagnetic and other magnetotransport effects
75.75.-c Magnetic properties of nanostructures

Spin-wave wells with multiple states created in small magnetic elements

C. Bayer, S. O. Demokritov, B. Hillebrands, and A. N. Slavin

Appl. Phys. Lett. 82, 607 (2003); http://dx.doi.org/10.1063/1.1540734 (3 pages) | Cited 40 times

Online Publication Date: 22 January 2003

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We have observed several localized modes in the spin-wave spectrum of a permalloy microstripe (length 90 μm, width 1 μm, thickness 0.033 μm) magnetized along its width. The mode frequencies increase from 4.5 to 8 GHz with increasing applied field (0–1.1 kOe). These modes are interpreted as multiple spin–wave eigenstates in effective potential wells created by a strongly inhomogeneous internal magnetic field in the stripe near its edges. © 2003 American Institute of Physics.
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75.30.Ds Spin waves
75.70.Ak Magnetic properties of monolayers and thin films
75.50.Bb Fe and its alloys
81.05.Bx Metals, semimetals, and alloys
75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)
76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance

Circular magnetic bistability induced by tensile stress in glass-covered amorphous microwires

A. Chizhik, J. Gonzalez, A. Zhukov, and J. M. Blanco

Appl. Phys. Lett. 82, 610 (2003); http://dx.doi.org/10.1063/1.1540735 (3 pages) | Cited 11 times

Online Publication Date: 22 January 2003

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Investigations of magnetic reversal in Co-rich glass covered amorphous microwires were performed using the magneto-optical Kerr-effect technique. The appearance of circular magnetic bistability was found in the presence of external tensile stress. A tensile-induced large Barkhausen jump of circular magnetization is associated with a change of the value of the magnetostriction constant induced by stress and by rearrangement of domain structure in the outer shell of the microwire. © 2003 American Institute of Physics.
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75.50.Kj Amorphous and quasicrystalline magnetic materials
81.07.Vb Quantum wires
78.20.Ls Magneto-optical effects
81.05.Bx Metals, semimetals, and alloys
75.80.+q Magnetomechanical effects, magnetostriction
75.75.-c Magnetic properties of nanostructures
78.67.Lt Quantum wires
75.60.Jk Magnetization reversal mechanisms
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.60.Ch Domain walls and domain structure

Large magnetoresistance in magnetically frustrated ruthenates

A. Mamchik and I.-W. Chen

Appl. Phys. Lett. 82, 613 (2003); http://dx.doi.org/10.1063/1.1540234 (3 pages) | Cited 7 times

Online Publication Date: 22 January 2003

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A large negative magnetoresistance effect is found in Fe-doped ruthenates of perovskite and layered perovskite structures. These new materials are magnetically glassy, and can be derived from a parent compound that is either magnetic or nonmagnetic. The magnetoresistance is nearly linear with the magnetic field up to 9 T and is stronger at lower temperature. Atomic-level spin valves associated with Fe cations on B sites that regulate electron transport in response to an external magnetic field are suggested to be the mechanism responsible. © 2003 American Institute of Physics.
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75.47.Pq Other materials
72.20.My Galvanomagnetic and other magnetotransport effects
75.50.Lk Spin glasses and other random magnets
75.50.Dd Nonmetallic ferromagnetic materials
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
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Single-crystal barium titanate thin films by ion slicing

T. Izuhara, I.-L. Gheorma, R. M. Osgood, A. N. Roy, H. Bakhru, Yiheli M. Tesfu, and M. E. Reeves

Appl. Phys. Lett. 82, 616 (2003); http://dx.doi.org/10.1063/1.1540727 (3 pages) | Cited 11 times

Online Publication Date: 22 January 2003

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Thin barium titanate films, 0.5–8 μm thick, are obtained from a single-crystal bulk sample using ion slicing. The process, based on ion implantation and anodic bonding, separates thin films having areas of ∼ 1×1 cm2, from bulk crystals. The quality of the film is characterized by measurement of surface roughness and dielectric properties. The film permittivity retains its single-crystal value. © 2003 American Institute of Physics.
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77.55.-g Dielectric thin films
61.80.Jh Ion radiation effects
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Gm Dielectric loss and relaxation
77.80.Dj Domain structure; hysteresis
61.82.Ms Insulators
61.72.up Other materials
68.35.B- Structure of clean surfaces (and surface reconstruction)
77.22.Ch Permittivity (dielectric function)
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)

Cylindroid rigid-wall simulation of the influence of gas pressure in pulsed laser deposition of LiNbO3 films

X. Yang, X. L. Wu, Z. Y. Zhang, G. G. Siu, Z. G. Dong, L. Fang, and M. R. Shen

Appl. Phys. Lett. 82, 619 (2003); http://dx.doi.org/10.1063/1.1540217 (3 pages)

Online Publication Date: 22 January 2003

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We have demonstrated that gas pressure (pG) is a key parameter for fabricating stoichiometric LiNbO3 thin films during laser ablation. To theoretically describe the influence of pG, a cylindroid rigid-wall model was presented. It was shown that there exist two critical pressures related to Li and Nb: pLi and pNb(pLi<pNb). They separate pG into three intervals. When pG<pLi, pG has little influence on film stoichiometry and the obtained films contain fixed Li deficiency. When pLi ⩽ pG ⩽ pNb, pG plays an important role in forming stoichiometric films. When pG ≥ pNb, the change of pG does not affect film stoichiometry, but the film growth because of greatly reduced energies of the species that reach the substrate. The presented theory was in good agreement with experiments. This model provides a useful way for growing multicomponent films by pulsed laser deposition. © 2003 American Institute of Physics.
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81.15.Fg Pulsed laser ablation deposition
68.55.A- Nucleation and growth
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
81.15.Aa Theory and models of film growth
77.55.-g Dielectric thin films
61.66.Bi Elemental solids
61.66.Dk Alloys
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Local probing of thermal properties at submicron depths with megahertz photothermal vibrations

M. Tomoda, N. Shiraishi, O. V. Kolosov, and O. B. Wright

Appl. Phys. Lett. 82, 622 (2003); http://dx.doi.org/10.1063/1.1539906 (3 pages) | Cited 2 times

Online Publication Date: 22 January 2003

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We demonstrate the imaging of buried features in a microstructure—a tiny hole in an aluminum thin film covered by a chromium layer—with nanometer lateral resolution using a transient temperature distribution restricted to within ∼0.5 μm of the sample surface. This is achieved by mapping photothermally induced megahertz surface vibrations in an atomic force microscope. Local thermal probing with megahertz-frequency thermal waves is thus shown to be a viable method for imaging subsurface thermal features at submicron depths. © 2003 American Institute of Physics.
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07.20.-n Thermal instruments and apparatus
78.20.N- Thermo-optic effects
78.20.nb Photothermal effects
68.35.Ja Surface and interface dynamics and vibrations
07.79.Lh Atomic force microscopes
68.37.Ps Atomic force microscopy (AFM)

Bias effect on the luminescent properties of rectangular and trapezoidal quantum-well structures

M. G. Cheong, R. J. Choi, E.-K. Suh, and H. J. Lee

Appl. Phys. Lett. 82, 625 (2003); http://dx.doi.org/10.1063/1.1536263 (2 pages) | Cited 3 times

Online Publication Date: 22 January 2003

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We have investigated the properties of two types of InGaN/GaN quantum-well (QW) structures. Photoluminescence (PL) measurements were carried out by varying the external bias voltage. The magnitude of the variation in PL peak position and intensity of trapezoid QWs (TQWs) is much smaller than that of rectangular QWs (RQWs). According to transmission electron microscopy measurements, quantum dots are more densely and uniformly distributed in TQWs than in RQWs. The electroluminescence image of a light-emitting diode fabricated using TQWs as active layers (TQW-LED) is more uniform than that of a light-emitting diode fabricated using RQWs as active layers (RQW-LED). Optical output power of a TQW-LED is larger than that of a RQW-LED. These results show that the origin of strong emission from InGaN/GaN QWs is attributed to exciton localization quantum dots, and InGaN/GaN TQWs are considered as active materials in order to increase performance in optoelectronic device. © 2003 American Institute of Physics.
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78.67.De Quantum wells
73.21.Fg Quantum wells
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
85.60.Jb Light-emitting devices
68.65.Fg Quantum wells
78.55.Cr III-V semiconductors
78.60.Fi Electroluminescence
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
71.35.Lk Collective effects (Bose effects, phase space filling, and excitonic phase transitions)

Luminescence polarization of ordered GaInP/InP islands

U. Håkanson, V. Zwiller, M. K.-J. Johansson, T. Sass, and L. Samuelson

Appl. Phys. Lett. 82, 627 (2003); http://dx.doi.org/10.1063/1.1539544 (3 pages) | Cited 3 times

Online Publication Date: 22 January 2003

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The luminescence polarization properties of GaInP islands have been investigated. The islands, which form during overgrowth of InP quantum dots, were studied using scanning tunneling luminescence (STL) and photoluminescence (PL). STL from these islands shows emission at an energy below the main emission peak of the bulk GaInP. The linear PL polarization anisotropy was measured at low temperature, for which the emission from the islands shows high polarization anisotropy. The intensity maximum for the emission occurs for light polarized parallel to the elongation of the islands. The observed linear PL polarization anisotropy indicates the presence of highly ordered domains of GaInP in the islands. © 2003 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
78.67.Hc Quantum dots

Response spectra from mid- to far-infrared, polarization behaviors, and effects of electron numbers in quantum-dot photodetectors

B. Aslan, H. C. Liu, M. Korkusinski, S.-J. Cheng, and P. Hawrylak

Appl. Phys. Lett. 82, 630 (2003); http://dx.doi.org/10.1063/1.1540728 (3 pages) | Cited 35 times

Online Publication Date: 22 January 2003

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Photoresponse characteristics of InAs/GaAs self-assembled quantum-dot infrared photodetectors in a wide spectral region from the mid- to far-infrared are reported. Clear polarization behaviors with a dominant P-polarized response in the mid-infrared and a strong S-response in the far infrared are shown. These behaviors can be qualitatively understood in view of the quantum-dot shape of a large in-plane diameter and a small height in the growth direction. With a set of three samples, effects of the number of electrons per dot on the spectra are investigated.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
81.07.Ta Quantum dots
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
78.67.Hc Quantum dots
73.21.La Quantum dots
81.05.Ea III-V semiconductors
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Investigation of buffer traps in an AlGaN/GaN/Si high electron mobility transistor by backgating current deep level transient spectroscopy

M. Marso, M. Wolter, P. Javorka, P. Kordoš, and H. Lüth

Appl. Phys. Lett. 82, 633 (2003); http://dx.doi.org/10.1063/1.1540239 (3 pages) | Cited 8 times

Online Publication Date: 22 January 2003

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The influence of a substrate voltage on the dc characteristics of an AlGaN/GaN high electron mobility transistor (HEMT) on silicon (111) substrate is profited to investigate traps that are located between the substrate and the two-dimensional electron gas channel. The transient of the drain current after applying a negative substrate voltage is evaluated in the temperature range from 30 to 100 °C. With this method, known as backgating current deep level transient spectroscopy, majority carrier traps with activation energy of 200 meV as well as minority carrier traps at 370 meV are identified. The experiments are performed on completed HEMTs, allowing the investigation of the influence of device fabrication technology. © 2003 American Institute of Physics.
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85.30.Tv Field effect devices
85.30.De Semiconductor-device characterization, design, and modeling
71.55.Eq III-V semiconductors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
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