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7 Jan 2002

Volume 80, Issue 1, pp. 1-162

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Measurement of true spontaneous emission spectra from the facet of diode laser structures

G. M. Lewis, P. M. Smowton, J. D. Thomson, H. D. Summers, and P. Blood

Appl. Phys. Lett. 80, 1 (2002); http://dx.doi.org/10.1063/1.1428774 (3 pages) | Cited 23 times

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Measurement of the spontaneous emission and gain spectra provides a complete characterization of a semiconductor gain medium, however, this requires the observation of emission in two directions to avoid amplification of the spontaneous emission spectrum. We show that both the gain spectrum and the true spontaneous emission spectrum can be obtained from amplified spontaneous emission (ASE) spectra measured from the end of a segmented-contact device. The spontaneous emission spectra agree with spectra measured through a top contact window. If the carrier populations are fully inverted at low photon energy, it is possible to convert the ASE-derived spontaneous emission into real units. © 2002 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
78.67.De Quantum wells
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
78.45.+h Stimulated emission

Electrochromic semiconductor nanocrystal films

Congjun Wang, Moonsub Shim, and Philippe Guyot-Sionnest

Appl. Phys. Lett. 80, 4 (2002); http://dx.doi.org/10.1063/1.1430852 (3 pages) | Cited 36 times

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Electron injection into nanocrystal thin films is reversibly controlled by applying an electrochemical potential. Complete bleach of the visible interband transition and strong midinfrared intraband absorption are observed upon electron injection into the nanocrystal films. Quenching of the photoluminescence of the nanocrystal film is also observed. © 2002 American Institute of Physics.
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78.66.Hf II-VI semiconductors
78.55.Et II-VI semiconductors
78.40.Fy Semiconductors
78.20.Jq Electro-optical effects

Laser emission from high-gain media of dye-doped dendrimer

Shiyoshi Yokoyama, Akira Otomo, and Shinro Mashiko

Appl. Phys. Lett. 80, 7 (2002); http://dx.doi.org/10.1063/1.1431400 (3 pages) | Cited 24 times

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We prepared high-gain media for laser emission by using a conventional laser-dye (DCM) and dendrimer. A dendrimer can encapsulate the laser dye, and therefore increase its concentration up to 9.0 mM with limited self-aggregation and intermolecular quenching. The optical confinement is attributed to gain guiding under optical excitation. The laser spectrum clearly indicated periodic resonant modes though the laser feedback was caused in an unusual way. Above the lasing threshold, the spectral linewidth became less than 0.1 nm. The laser-dye-doped dendrimer showed a particular ability to decrease the lasing threshold intensity by increasing the dye concentration. © 2001 American Institute of Physics.
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42.55.Mv Dye lasers
42.70.Hj Laser materials

Influence of molecular weight on the photorefractivity of polymer/liquid crystal composites

Yaowen Bai, Xiaofang Chen, Xinhua Wan, Qi-feng Zhou, Hui Liu, Bo Zhang, and Qihuang Gong

Appl. Phys. Lett. 80, 10 (2002); http://dx.doi.org/10.1063/1.1427427 (3 pages) | Cited 7 times

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We report on photorefractive composites composed of poly(N-vinyl carbazole) (PVK)/liquid crystal/C60 with PVK of different molecular weight (MW). The influence of MW on the photorefractivity was studied. The results show that a higher MW leads to a larger two-beam coupling coefficient Γ and a larger effective electric–optical coefficient. Γ over 200 cm−1 is observed for the composite based on the highest MW PVK. © 2002 American Institute of Physics.
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42.70.Gi Light-sensitive materials
42.70.Jk Polymers and organics
42.70.Df Liquid crystals
78.20.Jq Electro-optical effects
61.30.Vx Polymer liquid crystals

Enhanced performance of organic light-emitting devices by atmospheric plasma treatment of indium tin oxide surfaces

I-Min Chan, Weng-Cheng Cheng, and Franklin C. Hong

Appl. Phys. Lett. 80, 13 (2002); http://dx.doi.org/10.1063/1.1428624 (3 pages) | Cited 33 times

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Atmospheric plasma treatment of indium tin oxide (ITO) surfaces has been studied and demonstrated to be the most efficient method in improving the performance of vacuum-deposited double-layer organic light-emitting diode devices, among various plasma treatment methods including low-pressure Ar plasma and low-pressure O2 plasma treatment. Although with a current–voltage characteristic close to low-pressure O2 plasma treatment, the atmospheric plasma treatment exhibits a 40% increase of electroluminescence efficiency. X-ray photoelectron spectroscopy results show that the atmospheric plasma treatment increases the work function and reduces the carbon contamination of ITO surfaces. Our results suggest that atmospheric plasma treatment is a cheaper, more convenient, and more efficient method than low-pressure O2 plasma treatment for improving device performance. © 2002 American Institute of Physics.
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85.60.Jb Light-emitting devices
81.05.Hd Other semiconductors
81.65.-b Surface treatments
52.77.Bn Etching and cleaning
73.30.+y Surface double layers, Schottky barriers, and work functions
79.60.Bm Clean metal, semiconductor, and insulator surfaces

Polar diffraction gratings made by spatially periodic photopoling Langmuir–Blodgett films

L. M. Blinov, S. P. Palto, S. G. Yudin, M. P. De Santo, G. Cipparrone, A. Mazzulla, and R. Barberi

Appl. Phys. Lett. 80, 16 (2002); http://dx.doi.org/10.1063/1.1431399 (3 pages) | Cited 4 times

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Polar diffraction gratings have been prepared by spatially periodic photopoling Langmuir–Blodgett films consisting of azobenzene compounds. The gratings were made by film irradiation with two left circularly polarized Ar-ion laser beams under strong electric field from a corona discharge. Therefore, simultaneously with the spatial modulation of the linear refractive index, the local polar order of the film becomes periodically modulated (through symmetry, the latter is related to the modulation of second-order optical nonlinearity χ(2)). The local polarity is shown by an electrostatic force microscopy technique: an image of the polar grating is recorded without any trace of periodicity in the film topography. © 2002 American Institute of Physics.
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42.79.Dj Gratings
68.47.Pe Langmuir-Blodgett films on solids; polymers on surfaces; biological molecules on surfaces
78.66.Qn Polymers; organic compounds

Longitudinal carrier density measurement of high power broad area laser diodes

F. Rinner, J. Rogg, P. Friedmann, M. Mikulla, G. Weimann, and R. Poprawe

Appl. Phys. Lett. 80, 19 (2002); http://dx.doi.org/10.1063/1.1430264 (3 pages) | Cited 15 times

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The longitudinal carrier density distribution of an InGaAlAs high-power broad-area semiconductor laser has been measured using spontaneous emission from the side of the device. The laser shows continuously increasing carrier densities on the facet with the high reflectivity coating (reverse facet). This has a major impact on the efficiency and the lifetime of the laser. This behavior is in good agreement with one-dimensional calculations for the longitudinal carrier distribution. © 2002 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
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Control and mass selection of CnHm+ fragments in an inductively coupled pulsed plasma

D. A. Zeze, A. M. Joyce, C. A. Anderson, and N. M. D. Brown

Appl. Phys. Lett. 80, 22 (2002); http://dx.doi.org/10.1063/1.1428776 (3 pages) | Cited 4 times

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We report on a method of selecting CnHm+ fragments using a pulsed inductively coupled plasma (ICP) driven by a rf supply and a pulse control unit providing user-defined on/off regimes. Langmuir probe and mass-energy spectrometric data show that the characteristics of the plasma can be monitored so demonstrating that hydrocarbon clusters of different C:H ratios and abundances can be generated preferentially by using appropriately chosen on/off regimes. Postdeposition x-ray photoelectron spectroscopy (XPS) analysis underlines clearly the influence of the deposition regimes, on the structure and composition of CxNy:H films grown via CnHm+ clusters generated using adamantane (C10H16) vapor in an argon/nitrogen mixture. © 2002 American Institute of Physics.
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52.70.Nc Particle measurements
52.77.Dq Plasma-based ion implantation and deposition
52.70.Ds Electric and magnetic measurements
52.50.Dg Plasma sources
52.25.Fi Transport properties
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)
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Material-specific mapping of metal/semiconductor/dielectric nanosystems at 10 nm resolution by backscattering near-field optical microscopy

R. Hillenbrand and F. Keilmann

Appl. Phys. Lett. 80, 25 (2002); http://dx.doi.org/10.1063/1.1428767 (3 pages) | Cited 7 times

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We report that three main constituents of nanosystems—metals, semiconductors, and dielectrics—can be categorically distinguished by their specific optical near-field contrast at 633 nm wavelength. The decisive property is the local dielectric constant as we show by calculations based on dipolar coupling theory. Experiments with Au/Si/PS(polystyrene) nanostructures using an apertureless scattering-type near-field optical microscope yield optical images at 10 nm resolution, with clear material contrast close to predicted levels. © 2002 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
78.67.-n Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures
68.37.Uv Near-field scanning microscopy and spectroscopy
07.79.Fc Near-field scanning optical microscopes
68.35.B- Structure of clean surfaces (and surface reconstruction)
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Specific heat and thermodynamic properties of undercooled liquid cobalt

N. Wang, X. J. Han, and B. Wei

Appl. Phys. Lett. 80, 28 (2002); http://dx.doi.org/10.1063/1.1428409 (3 pages) | Cited 18 times

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Co is undercooled to 227 K (0.128 Tm) and its specific heat has been determined as 40.6 Jmol−1 K−1 by electromagnetic levitation drop calorimeter, whose good accuracy is verified by the measured specific heat data of pure nickel. On the basis of measured specific heat data, the thermodynamic properties, such as thermodynamic driving force and relative nucleation rate, are calculated. Moreover, the theoretical models of Turnbull and Dubey–Ramachandrarao are also used to calculate the thermodynamic properties for a comparison. It is found that both the thermodynamic driving force and relative nucleation rate have large deviation compared with the calculated results based on experimental data. This indicates that, since the deviation of specific heat value has a drastic influence on thermodynamic driving force and nucleation rate for the undercooled liquid metals, it is necessary to measure the specific heat quantitatively by experiments. © 2002 American Institute of Physics.
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65.20.-w Thermal properties of liquids

Effect of electron irradiation on the transformation characteristics of narrow hysteresis TiNiCu shape memory alloys

X. T. Zu, L. M. Wang, Y. Huo, L. B. Lin, Z. G. Wang, T. C. Lu, L. J. Liu, and X. D. Feng

Appl. Phys. Lett. 80, 31 (2002); http://dx.doi.org/10.1063/1.1427747 (3 pages) | Cited 10 times

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TiNiCu shape memory alloy samples were irradiated by 1.7 MeV electrons below the martensite finish temperature Mf. The transformation temperatures and the latent heat of phase transformation were measured by differential scanning calorimeter. The damage accumulation was determined by positron annihilation technology. The results indicated that the austenite transformation temperatures were raised, and the hysteresis was increased by the irradiation. The electron irradiation had a slight effect on Mf, and no detectable effect on the martensitic transformation start temperature Ms. The second lifetime of positrons were increased by the electron irradiation indicating the increase in the size and amount of vacancy clusters, which contributed to the observed change of the transformation characteristics. © 2002 American Institute of Physics.
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81.30.Kf Martensitic transformations
61.80.Fe Electron and positron radiation effects
64.70.K- Solid-solid transitions
78.70.Bj Positron annihilation
82.60.Fa Heat capacities and heats of phase transitions

Band anticrossing effects in MgyZn1−yTe1−xSex alloys

J. Wu, W. Walukiewicz, K. M. Yu, J. W. Ager, W. Shan, E. E. Haller, I. Miotkowski, A. K. Ramdas, and S. Miotkowska

Appl. Phys. Lett. 80, 34 (2002); http://dx.doi.org/10.1063/1.1430853 (3 pages) | Cited 6 times

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The electronic structures of MgyZn1−yTe1−xSex alloys were studied by optical absorption and photoluminescence techniques under applied hydrostatic pressure. In samples with both x and y ≠ 0, the band gap exhibits a strongly nonlinear pressure dependence which is similar to the effects observed previously in ZnTe1−xSex and ZnTe1−xSx ternaries and that is well explained by the anticrossing interaction of the selenium localized electronic states with the conduction band of the matrix. In contrast, the pressure dependence of the band gap in MgyZn1−yTe (i.e., x = 0) is not significantly changed in form from that of ZnTe; it is concluded that the effects of alloying MgTe with ZnTe can be well understood within the virtual crystal approximation. © 2002 American Institute of Physics.
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71.20.Nr Semiconductor compounds
78.40.Fy Semiconductors
78.55.Et II-VI semiconductors

Efficient 230–280 nm emission from high-Al-content AlGaN-based multiquantum wells

Hideki Hirayama, Yasushi Enomoto, Atsuhiro Kinoshita, Akira Hirata, and Yoshinobu Aoyagi

Appl. Phys. Lett. 80, 37 (2002); http://dx.doi.org/10.1063/1.1432112 (3 pages) | Cited 25 times

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We demonstrated efficient ultraviolet (UV) photoluminescence (PL) with the wavelength ranging from 230 to 280 nm from AlxGa1−xN(AlN)/AlyGa1−yN multiquantum wells (MQWs) grown on SiC by metalorganic vapor phase epitaxy. We systematically investigated the PL intensity of the AlGaN-based MQWs with wide-band-gap AlGaN barriers as functions of QW thickness and Al content of barriers. Single-peak, efficient PL emission was obtained at 282–234 nm at 77 K from AlxGa1−xN(AlN)/AlyGa1−yN 5-layer MQWs with approximately 1.5-nm-thick active layers by changing the Al content of the AlxGa1−xN barriers from 53% to 100%. The efficiency of the deep-UV emission from AlGaN-based QWs was as high as that of blue emission from InGaN-based QWs at 77 K. © 2002 American Institute of Physics.
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78.67.De Quantum wells
78.55.Cr III-V semiconductors

Nanovoid-related large redshift of photoluminescence peak energy in hydrogenated amorphous silicon

Daxing Han, Guozhen Yue, Keda Wang, Jonathan Baugh, Yue Wu, Yueqin Xu, and Qi Wang

Appl. Phys. Lett. 80, 40 (2002); http://dx.doi.org/10.1063/1.1431396 (3 pages) | Cited 5 times

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A large redshift of the photoluminescence (PL) peak energy is found in hydrogenated amorphous silicon films prepared by hot-wire chemical-vapor deposition with a high-growth rate ⩾50 Å/s. The PL intensity is as high as that in the standard film and its temperature dependence shows thermalization behavior. The origin of the redshift is clarified by employing 1H nuclear magnetic resonance and mass density measurements. A ∼2% volume fraction of tube-like nanoscale voids is identified. The long spin-lattice relaxation time of H2 in the nanovoids implies a negligible density of silicon dangling bonds on the nanovoid surfaces. We suggest that highly strained bonds on these surfaces form broad conduction-band tail states that are responsible for the PL redshift. © 2002 American Institute of Physics.
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78.55.Ap Elemental semiconductors
61.72.Qq Microscopic defects (voids, inclusions, etc.)
78.66.Db Elemental semiconductors and insulators
78.66.Jg Amorphous semiconductors; glasses
76.60.Es Relaxation effects

Multilayer-array growth of SiGeC alloys on Si(001)

Vinh LeThanh, C. Calmes, Y. Zheng, and D. Bouchier

Appl. Phys. Lett. 80, 43 (2002); http://dx.doi.org/10.1063/1.1428631 (3 pages) | Cited 5 times

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The growth of SiGeC alloys on Si(001) in an ultrahigh vacuum chemical-vapor deposition system was investigated by means of in situ reflection high-energy electron diffraction, transmission electron microscopy, and high resolution x-ray diffraction. It is shown that when the total amount of deposited carbon exceeds a value of about 1.5%, the grown layers contain a high density of stacking faults and/or microtwins. However, such defects are found to be formed only after the deposition of a certain thickness, whose value depends on the deposited carbon amount. By realizing SiGeC/Si multilayer arrays, we show that defect-free SiGeC films with a substitutional carbon content up to 3.3% can be achieved. © 2002 American Institute of Physics.
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68.65.Ac Multilayers
61.72.Mm Grain and twin boundaries
61.72.Nn Stacking faults and other planar or extended defects
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Orientation effects in tBN/cBN interfaces: A transmission electron microscopic study

Quan Li, I. Bello, L. D. Marks, Y. Lifshitz, and S. T. Lee

Appl. Phys. Lett. 80, 46 (2002); http://dx.doi.org/10.1063/1.1431394 (3 pages) | Cited 8 times

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The orientation between cubic boron nitride (cBN) crystallites and the tBN layers on which they grow was studied using high-resolution transmission electron microscopy. BN films were prepared by radio-frequency magnetron sputtering under conditions leading to the formation of ∼100% cBN films grown on a preceding tBN layer. Two types of orientations were observed: (i) cBN layers grown on the edges of the tBN(0002) planes so that the cBN{111} planes are parallel to the tBN(0002) planes (as reported previously by many authors), (ii) cBN layers grown on curved tBN(0002) planes with no orientation to the tBN planes. The first type of cBN growth is associated with stress leading to delamination of cBN films thicker than 100 nm. The second type is associated with reduced stress enabling the growth of much thicker (∼500 nm) films at a relatively low (450 °C) substrate deposition temperature. These results may be helpful in the fabrication of thick cBN films and improving our understanding of the cBN nucleation process. © 2002 American Institute of Physics.
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68.35.Ct Interface structure and roughness
68.37.Lp Transmission electron microscopy (TEM)
81.15.Cd Deposition by sputtering

Photonic crystals of core-shell colloidal particles

Krassimir P. Velikov, Alexander Moroz, and Alfons van Blaaderen

Appl. Phys. Lett. 80, 49 (2002); http://dx.doi.org/10.1063/1.1431698 (3 pages) | Cited 54 times

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We report on the fabrication and optical transmission studies of thin three-dimensional photonic crystals of high-dielectric ZnS-core and low-dielectric SiO2-shell colloidal particles. These samples were fabricated using a vertical controlled drying method. The spectral position and width of a stopgap depend on the core-to-shell ratio, in a manner consistent with numerical calculations. Both experiments and calculations show that the relative L-stopgap width in the case of high-index core low-index shell particles can be larger in comparison to the case of homogeneous particles of either material. The core-shell morphology gives additional control over the photonic stopgap characteristics. © 2002 American Institute of Physics.
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42.70.Qs Photonic bandgap materials
82.70.Dd Colloids

Ab initio modeling and experimental study of C–B interactions in Si

Chun-Li Liu, Wolfgang Windl, Len Borucki, Shifeng Lu, and Xiang-Yang Liu

Appl. Phys. Lett. 80, 52 (2002); http://dx.doi.org/10.1063/1.1430505 (3 pages) | Cited 12 times

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We present results of ab initio calculations for the structure and energetics of small boron-carbon-interstitial and carbon-interstitial clusters in silicon and a respective continuum model for the nucleation, growth, and dissolution of these clusters. To test our calculations, we also measure secondary-ion mass spectra of boron and carbon in a SiGeCB system, which our model reproduces well. For the considered concentration regime, we find rapid carbon diffusion, nearly immobile boron, and undersaturation of silicon self-interstitials, resulting mainly from two clusters suggested by our ab initio results, the dicarbon-interstitial cluster and the boron-carbon-interstitial cluster. © 2002 American Institute of Physics.
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61.72.Yx Interaction between different crystal defects; gettering effect
61.72.J- Point defects and defect clusters
66.30.J- Diffusion of impurities
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
31.15.A- Ab initio calculations

Growth of low-stress cubic boron nitride films by simultaneous medium-energy ion implantation

C. Fitz, A. Kolitsch, W. Möller, and W. Fukarek

Appl. Phys. Lett. 80, 55 (2002); http://dx.doi.org/10.1063/1.1430268 (3 pages) | Cited 15 times

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It is demonstrated that the intrinsic stress in cubic boron nitride films can be significantly relaxed during growth by simultaneous medium-energy ion implantation. The stress in the growing film has been studied in situ using cantilever curvature measurements and has been reduced to below 2 GPa by simultaneous Ar+ or N+ ion implantation with an energy of 70 and 35 keV, respectively. The resulting cubic boron nitride films show an increased long-term stability. The results reveal that the stress in cBN is not reduced due to segregation of boron at grain boundaries. © 2002 American Institute of Physics.
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68.55.A- Nucleation and growth
61.72.up Other materials
68.60.Bs Mechanical and acoustical properties
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances

Optical gaps of ab initio generated random networks for a-SiNx alloys

Fernando Alvarez and Ariel A. Valladares

Appl. Phys. Lett. 80, 58 (2002); http://dx.doi.org/10.1063/1.1430271 (3 pages) | Cited 7 times

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We report optical gaps for ab initio generated random networks of silicon–nitrogen alloys, a-SiNx, for thirteen values of x from 0 to x = 1.29, a nearly stoichiometric composition. The random networks were constructed by amorphizing 64-atom periodically-continued diamond-like cells containing silicon and nitrogen, with a new thermal process and a Harris-functional based molecular dynamics code in the local density approximation. The electron energy levels were then calculated and the optical gaps obtained using a Tauc-like procedure that is not sensitive to gap states and band tails. Our results agree with experiment. © 2002 American Institute of Physics.
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78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
71.15.Pd Molecular dynamics calculations (Car-Parrinello) and other numerical simulations
71.23.Cq Amorphous semiconductors, metallic glasses, glasses

Vapor–liquid–solid tri-phase pulsed-laser epitaxy of RBa2Cu3O7−y single-crystal films

K. S. Yun, B. D. Choi, Y. Matsumoto, J. H. Song, N. Kanda, T. Itoh, M. Kawasaki, T. Chikyow, P. Ahmet, and H. Koinuma

Appl. Phys. Lett. 80, 61 (2002); http://dx.doi.org/10.1063/1.1432111 (3 pages) | Cited 19 times

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We report on the fabrication of single-crystalline thin films of RBa2Cu3O7−y (R: rare-earth element, R123) using an approach of vapor–liquid–solid tri-phase epitaxy. This method is based on application of pulsed-laser deposition under appropriate compositions and conditions predetermined from the relevant thermodynamic phase diagram. The laser-ablated gases of R, Ba, and Cu, and their oxides dissolve into a liquid Ba3Cu5Ox (3BaCuO2+2CuO) layer placed on the film/substrate surface, penetrate to reach the liquid–solid interface with a seed R123, and are condensed into the solid R123 phase under a quasiequilibrium state. The uniform single-crystalline nature of the film was verified by x-ray diffraction, atomic-force microscopy, and transmission electron microscopy by the observation of giant grain size and atomic-scale surface smoothness. © 2002 American Institute of Physics.
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74.78.-w Superconducting films and low-dimensional structures
81.15.Fg Pulsed laser ablation deposition
68.55.-a Thin film structure and morphology
74.72.-h Cuprate superconductors
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.37.Lp Transmission electron microscopy (TEM)
68.37.Ps Atomic force microscopy (AFM)
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Effect of scattering by strain fields surrounding edge dislocations on electron transport in two-dimensional electron gases

Debdeep Jena and U. K. Mishra

Appl. Phys. Lett. 80, 64 (2002); http://dx.doi.org/10.1063/1.1429758 (3 pages) | Cited 17 times

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We present a theory of deformation potential carrier scattering of two-dimensional electron gases from the strain fields surrounding edge dislocations. The scattering rate is evaluated in closed form without any fitting parameters. The result is directed towards understanding mobility limiting scattering mechanisms for two-dimensional electron gases at AlGaN/GaN heterointerfaces. © 2002 American Institute of Physics.
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72.10.Fk Scattering by point defects, dislocations, surfaces, and other imperfections (including Kondo effect)
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.50.Dn Low-field transport and mobility; piezoresistance
73.61.Ey III-V semiconductors

Engineering of Si surfaces by electrochemical grafting of p-nitrobenzene molecules

P. Hartig, J. Rappich, and Th. Dittrich

Appl. Phys. Lett. 80, 67 (2002); http://dx.doi.org/10.1063/1.1430265 (3 pages) | Cited 16 times

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The changes of the band bending and of the nonradiative (nr) surface recombination are investigated by use of photovoltage and photoluminescence techniques during the electrochemical deposition of p-nitrobenzene molecules on atomically flat and rough hydrogenated as well as on chemically oxidized Si(111) surfaces. A simple and well-reproducible procedure has been developed for electrochemical grafting of organic molecules on hydrogenated Si surfaces in aqueous electrolytes. The grafting of a monolayer of p-nitrobenzene molecules on atomically flat p-Si(111):H surfaces induces a change of the band bending of about 0.1 eV and the amount of nr surface defects, Ns, is only slightly increased by a factor of about 3 (Ns<1011 cm−2) with respect to the hydrogenated Si surface. The role of the formation of radicals for the engineering of Si surfaces is discussed. © 2002 American Institute of Physics.
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73.20.Hb Impurity and defect levels; energy states of adsorbed species
73.25.+i Surface conductivity and carrier phenomena
78.68.+m Optical properties of surfaces
81.15.Pq Electrodeposition, electroplating
72.40.+w Photoconduction and photovoltaic effects
78.55.Ap Elemental semiconductors
82.45.Qr Electrodeposition and electrodissolution

Determination of charge carrier concentration in n- and p-doped SiC based on optical absorption measurements

R. Weingärtner, P. J. Wellmann, M. Bickermann, D. Hofmann, T. L. Straubinger, and A. Winnacker

Appl. Phys. Lett. 80, 70 (2002); http://dx.doi.org/10.1063/1.1430262 (3 pages) | Cited 17 times

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We have investigated the effect of doping on absorption for various SiC polytypes, i.e., n-type (N) 6H–SiC, 4H–SiC, and 15R–SiC, p-type (Al) 6H–SiC, and 4H–SiC, and p-type (B) 6H–SiC. For these polytypes the band-gap narrowing with higher doping concentration is observed. In addition, for n-type doping below band-gap absorption bands at 464 nm for 4H–SiC, at 623 nm for 6H–SiC, and at 422 and 734 nm for 15R–SiC are observed. The peak intensities of these absorption bands show a linear relation to the charge carrier concentration obtained from Hall measurements. The corresponding calibration factors are given. As an application a purely optical wafer mapping of the spatial variation of the charge carrier concentration is demonstrated. © 2002 American Institute of Physics.
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Chemical profiling of single nanotubes: Intramolecular p–n–p junctions and on-tube single-electron transistors

Jing Kong, Jien Cao, Hongjie Dai, and Erik Anderson

Appl. Phys. Lett. 80, 73 (2002); http://dx.doi.org/10.1063/1.1431402 (3 pages) | Cited 44 times

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Electrical transport properties of intramolecular p–n–p junctions formed on individual semiconducting carbon nanotubes are reported. Chemical dopant “profiling” along the length of a nanotube divides the nanotube into two p-doped sections and a central n-doped section. The double p–n junctions formed on the nanotube dictate the electrical characteristics of the system. Well-defined and highly reproducible single-electron transistors with much smaller size than the geometrical length of the nanotube are obtained. © 2002 American Institute of Physics.
Show PACS
85.35.Kt Nanotube devices
61.72.S- Impurities in crystals
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
85.35.Gv Single electron devices
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