Bulletin of the American Physical Society
2009 APS March Meeting
Volume 54, Number 1
Monday–Friday, March 16–20, 2009; Pittsburgh, Pennsylvania
Session V21: Semiconductor Growth and Material Processing |
Hide Abstracts |
Sponsoring Units: FIAP Chair: Nelson Tansu, Lehigh University Room: 323 |
Thursday, March 19, 2009 8:00AM - 8:12AM |
V21.00001: Gallium beam analysis and implications for the growth of ultra-pure GaAs/AlGaAs heterostructures Stefan Schmult, Sam Taylor, Werner Dietsche The low temperature mobility of a two-dimensional electron gas (2DEG) is a perfect probe of the residual level of charged impurities in GaAs/AlGaAs heterostructures grown by molecular beam epitaxy (MBE) [1]. Besides the need of an ultra-high vacuum environment to prevent impurity incorporation during the growth process, pollution may still result from the source materials themselves. We evaluate the purity of Gallium by channeling the evaporated beam through the detection head of a mass spectrometer mounted in cross-beam geometry. It is found, that at the beginning of a growth campaign Gallium-Oxygen and Gallium-Hydrogen compounds represent the sole contaminations resulting from above-average MBE-grade Gallium at our present detection sensitivity [2]. Utilizing the aforementioned Gallium, we obtain in simple single-interface heterostructures 2DEG mobilities exceeding 10$^{7}$cm$^{2}$/Vs. This value is not limited by charged residual impurities, as confirmed in 2DEG-density-dependent transport measurements. [1] F. Stern, Appl. Phys. Lett. \textbf{43}, 974, (1983). [2] S. Schmult, et al., J. Crystal Growth (2008), doi:10.1016/j.jcrysgro.2008.10.014. [Preview Abstract] |
Thursday, March 19, 2009 8:12AM - 8:24AM |
V21.00002: Crystal orientation control of CdTe epitaxial layers grown on (100) GaAs with ZnSe buffer layer by molecular beam epitaxy Qiang Zhang, William Charles, Bingsheng Li, Aidong Shen, Carlos Meriles, Maria Tamargo Based on our previous experience with the growth of ZnSe on GaAs, we have improved the substrate, on which we deposit CdTe by first depositing a ZnSe buffer on the bulk GaAs crystals. This allows us to control the II-VI/III-V heterovalent epitaxy prior to the CdTe deposition. Depending on the control of the interface between ZnSe and CdTe, it was possible to stabilize the growth of either (100) or (111) CdTe epitaxial layers on the (100) ZnSe/GaAs substrate. Reflection high-energy electron diffraction was used to observe the nucleation of the epitaxial layers in situ during the growth, while x-ray diffraction and photoluminescence measurements indicate that the CdTe is of high structural quality despite the large lattice constant mismatch of 14.3{\%} between CdTe and ZnSe. To explore the full impact of controllable-orientation growth technique, optical pumping and time-resolved Faraday rotation experiments were performed on CdTe films grown in different crystal orientation. [Preview Abstract] |
Thursday, March 19, 2009 8:24AM - 8:36AM |
V21.00003: Development of a Wafer Fusion Process for Producing Patterned GaP Templates Krongtip Termkoa, Vaibhav Mathur, Xifeng Qian, William Goodhue, David Bliss, Rita Peterson Quasi-phase-matching (QPM) is an effective technique for nonlinear optical frequency conversion to generate IR wavelengths not readily available from direct laser sources. The QPM gratings can be produced by electric field poling in ferroelectric oxide materials, or by crystal growth of alternating phase domains in the case of semiconductors. For semiconductor materials GaAs and GaP we are developing new patterning methods to produce optical gratings for QPM. The state of the art for producing orientation-patterned GaAs material is already well developed. Gallium phosphide (GaP), also transparent at IR wavelengths, is attracting interest for nonlinear optical frequency conversion due to its high second-order nonlinear susceptibility, high thermal conductivity, wide band gap and low optical loss. Here we report a method to fabricate a GaP periodic domain inversion template using a process combining wafer fusion, substrate removal, lithographic patterning, and wet/dry etching. [Preview Abstract] |
Thursday, March 19, 2009 8:36AM - 8:48AM |
V21.00004: Growth of GaN from Ga:In and Ga:Sb liquid alloys Kathleen Kash, Challa Bekele, John Angus We grew GaN from Ga:Sn and Ga:In melt solutions that varied in composition from pure Ga to a few at{\%} Ga. Growth was done at 900 \r{ }C and 100 mtorr pressure by exposing the melt surface to a nitrogen plasma. A fit to a model of growth rate versus melt composition yielded estimates of the reaction rates for the formation of GaN versus composition of the melt that were, within experimental uncertainty, independent of the choice of diluent. Near-band-edge emission features were prominent in the photoluminescence spectra at both room temperature and 10 K for material grown from the entire range of melt compositions for both diluents. Lattice parameters measured by powder x-ray diffraction spectroscopy revealed an interesting dependence on melt composition; the ``a'' lattice parameter varied by as much as 1{\%} and exhibited a minimum for material grown from melts with compositions between 60 and 70 at{\%} Ga, for both diluents. One motivation for this work is growth of large area, high quality single crystal substrates. [Preview Abstract] |
Thursday, March 19, 2009 8:48AM - 9:00AM |
V21.00005: Epitaxial Growth and Characterization of Void-Free 3C-SiC Films on Germanium-Modified Si Substrates using RTCVD Domingo Ferrer, Shagandeep Kaur, Sayan Saha, Seyoung Kim, Emanuel Tutuc, Sanjay Banerjee, Nilratan Mazumder Cubic silicon carbide (3C-SiC) is an attractive wide band gap semiconductor, frequently employed under extreme conditions such as high temperature, high frequency and high power, due to its superior physical and chemical properties. The electronic properties of epitaxial graphene grown on SiC integrated on silicon substrates also offer great potential as a viable candidate for ``\textit{beyond CMOS''} devices. A detailed understanding of both the structure and growth of epitaxial graphene, and the SiC/Si interfaces is very important for designing feasible devices. To this end, the work will analyze the growth and characterization of 3C-SiC on Si(100) and Si(111) substrates. 3C--SiC epitaxial crystal growth was carried out at temperatures as low as 750$^{\circ}$C using Rapid Thermal CVD. A thin germanium buffer layer was deposited on Si substrates prior to epitaxial growth of SiC to suppress the formation of voids. The precursors utilized were (CH3)3SiH and GeH4, for silicon carbide and germanium deposition, respectively. [Preview Abstract] |
Thursday, March 19, 2009 9:00AM - 9:12AM |
V21.00006: The role of strontium in oxide epitaxy on silicon (001). James Reiner, Kevin Garrity, Fred Walker, Sohraib Ismail-Beigi, Charles Ahn The integration of crystalline oxides and semiconductors has been made possible by the development of techniques that allow crystalline SrTiO$_{3}$ to be grown on the silicon (001) surface. The most successful approach to realizing these epitaxial oxide-silicon (001) heterostructures requires manipulating substrate temperature and oxygen pressure on a layer-by-layer basis during the deposition of the metal oxide layers. The transition layer between the semiconductor and crystalline oxide is an alkaline earth metal, most often strontium, that is deposited on the silicon surface at around 650\r{ }C. Motivated by the desire to develop a fundamental understanding of this important transition layer, we have studied the surface structures formed by strontium on miscut silicon wafers, which, unlike regular silicon wafers, have a unique surface termination. At high temperatures, this reaction rearranges the top layer of silicon to replace the original top layer with strontium. At low temperatures, this reaction is suppressed, leading to a different, but symmetry related, ordered surface structure. We find that complex oxides can be grown on either surface with comparable crystallinity. [Preview Abstract] |
Thursday, March 19, 2009 9:12AM - 9:24AM |
V21.00007: ABSTRACT WITHDRAWN |
Thursday, March 19, 2009 9:24AM - 9:36AM |
V21.00008: Continuum model of surface roughness evolution of a-Si:H films grown by low-temperature PECVD Yevgen Kryukov, Nik Podraza, Robert Collins, Jacques Amar Using real-time spectroscopic ellipsometry the evolution of the surface roughness in a-Si:H thin-films grown on smooth c-Si/native oxide substrates by low-temperature plasma-enhanced chemical vapor deposition (PECVD) has been studied as a function of the $H_2$ dilution ratio $R = [H_2]/[SiH_4]$ with $15 \le R \le 60$. The best amorphous Si photovoltaic films correspond to a relatively high dilution ratio ($R \simeq 60$) such that the surface roughness is minimized but close to the amorphous-microcrystalline transition. After a brief period of nucleation of 3D islands, the roughness decreases but then eventually increases rapidly at large bulk layer thicknesses. Using a 3D continuum equation which includes a negative surface tension to take into account the destabilizing effects of short-range attraction and/or shadowing, as well as a smoothing term to take into account surface diffusion we have been able to obtain excellent agreement with experimental results for the evolution of the surface roughness. The dependence of our model parameters on the dilution ratio $R$ is also discussed. [Preview Abstract] |
Thursday, March 19, 2009 9:36AM - 9:48AM |
V21.00009: In-situ growth of two-terminal silicon nanowires from locally heated cantilevers Christian Kallesoe, Frances Ross, Chen-Yen Wen, Kristian Molhave, Peter Boggild Resistively heated crystalline silicon cantilevers extending over the edge of a chip offer excellent control of local growth of nanowires, without heating the entire micro-system. Besides being CMOS compatible, the cantilevers also have a rapid temperature cycling, and furthermore the freestanding cantilevers are suitable for in-situ studies of nanowire growth inside a TEM, offering the possibility of applying electrical fields to direct the growth and growing bridging wires between cantilevers thereby making two-terminal in-situ electrical measurements of nanowires possible. We have used such cantilever loops to study the growth of nanowires in-situ in UHVTEM. Epitaxial growth was observed from the crystalline cantilevers and the rapid temperature cycling ensured a very fast reaction time when crystallizing or melting the catalytic particle. The silicon wires were grown towards a cold cantilever loop, thereby forming bridging nanowires and the nanowire contact was seen to depend on the wetting ability of the gold catalytic particle to the cold cantilever. Furthermore various two-terminal measurements were performed on the bridging silicon nanowires in-situ in UHV. [Preview Abstract] |
Thursday, March 19, 2009 9:48AM - 10:00AM |
V21.00010: Time-Evolution of the Grain Size Distribution in Random Nucleation and Growth Crystallization Processes Andreas Bill, Anthony V. Teran, Ralf B. Bergmann The micromorphology of solids impacts in an essential way their mechanical, electronic, optical or magnetic properties. Hence, it is an important task to characterize properly the granularity of materials. One central quantity providing such information is the grain size distribution. We propose an analytical derivation of this distribution during the random nucleation and growth crystallization process of a $d-$dimensional solid ($d=1,2,3$). We describe how the grain size distribution evolves from early stages of crystallization to its final form when complete crystallization is achieved. We also discuss the remarkable result that for certain classes of nucleation and growth rates the asymptotic limit of large times is a logarithmic-normal (lognormal) type distribution. Finally, we apply the theory to the time-evolution of the grain size distribution during solid-phase crystallization of Si-films. [Preview Abstract] |
Thursday, March 19, 2009 10:00AM - 10:12AM |
V21.00011: ABSTRACT WITHDRAWN |
Thursday, March 19, 2009 10:12AM - 10:24AM |
V21.00012: Nanocrystalline Silicon Films by HWCVD Method Purabi Gogoi, Himanshu S. Jha, Pratima Agarwal High quality nano-crystallites embedded amorphous silicon films are deposited using HWCVD technique by varying the substrate temperature T$_{S}$ (100-350 $^{\circ}$C) and chamber pressure P (0.08-.8mbar). The precursor gas used is semiconductor grade hydrogen diluted silane (10 {\%} silane in hydrogen) from Matheson Inc. Filament temperature (T$_{F})$ is kept constant at 1800 $^{\circ}$C. The films are characterized by different tools viz. XRD, SEM, TEM, UV-Vis NIR spectroscopy, FTIR and PL. Both XRD and HRTEM studies indicate the presence of Nanocrystallite (size 5-10nm) in these films. The deposition rate ranges from 5-13 {\AA}/Sec, whereas the hydrogen content varies between 2.5-5 atomic percent. The band gap of films is in the range 2.0-2.37eV. Formation of Nanocrystallites is also supported by the PL and Raman scattering studies. Deposition rate decreases with increase in T$_{S}$, whereas the crystallinity increases with T$_{S}$. The films deposited at high pressure have high deposition rate, low hydrogen content and high band gap. The films are found to be of superior electronic properties suitable for photovoltaic device applications. The tunable band gap, high deposition rate and low hydrogen content is ideal for cost effective device fabrication. [Preview Abstract] |
Thursday, March 19, 2009 10:24AM - 10:36AM |
V21.00013: Growth and physical properties of epitaxial GdN and SmN Ben Ruck, Bart Ludbrook, Joe Trodahl, Andrew Preston, Claire Meyer, Ian Farrell, Steve Durbin, Roger Reeves, Matthias Kubel, Laurent Ranno The epitaxial growth and passivation of GdN and SmN by pulsed laser deposition on [100] YSZ substrates has been refined. We report on the growth kinetics, including the relaxation of the films, and the incorporation of oxygen at the substrate-film interface. Magnetic susceptibility measurements confirm a Tc of 70K and small coercive field for GdN. Resistivity measurements show an anomalous peak at Tc, while magnetic transport measurements indicate the films are electron doped to degeneracy, and show a strong anomalous Hall contribution below Tc. [Preview Abstract] |
Thursday, March 19, 2009 10:36AM - 10:48AM |
V21.00014: Synthesis and Magnetism of High Curie Temperature Prussian Blue Analogue Molecular Nanomagnet-Chromium Cyanide Molecule Nanowire Arrays Pingheng Zhou, Desheng Xue, Jinli Yao The goal to synthesize molecular nanomagnets that exhibit spontaneous magnetic ordering close to room temperature might enable one to apply them in the fields of magnetic memory devices and microelectronics. Chromium cyanide molecule nanowire arrays with diameters of about 50 nm and lengths up to 4$\mu $m have been synthesized by an electrodepositing technology based on anodizing anodic aluminum oxide films. Characterization measurements show that the oxidation state of the chromium ions in the chromium cyanide nanowires can be expressed as Cr$^{3+}$--CN--Cr$^{3+}$. Magnetic properties measurements indicate that the Curie temperature of chromium cyanide nanowire is 200 K, which is closer room temperature compared with current molecular nanomagnet systems. [Preview Abstract] |
Thursday, March 19, 2009 10:48AM - 11:00AM |
V21.00015: ABSTRACT WITHDRAWN |
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