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1.
Jacobs R. N. Stoltz A. J. Robinson E. W. Boyd P. R. Almeida L. A. Dinan J. H. Salamanca-Riba L. 《Journal of Electronic Materials》2004,33(6):538-542
The vision of achieving a completely in-vacuum process for fabricating HgCdTe detector arrays is contingent on the availability
of a vacuumcompatible photolithography technology. One such technology for vacuum photolithography involves the use of amorphous-hydrogenated
Si (a-Si:H) as a photoresist. In this work, we deposit a-Si:H resists via plasma-enhanced chemical-vapor deposition (PECVD)
using an Ar-diluted silane precursor. The resists are then patterned via excimer laser exposure and development etched in
a hydrogen plasma where etch selectivities between unexposed and exposed regions exceed 600:1. To determine the best conditions
for the technique, we investigate the effects of different exposure environments and carry out an analysis of the a-Si:H surfaces
before and after development etching. Analysis via transmission electron microscopy (TEM) reveals that the excimer-exposed
surfaces are polycrystalline in nature, indicating that the mechanism for pattern generation in this study is based on melting
and crystallization. To demonstrate pattern transfer, underlying CdTe films were etched (after development of the resist)
in an electron cyclotron resonance (ECR) plasma, where etch selectivities of approximately 8:1 have been achieved. The significance
of this work is the demonstration of laser-induced poly-Si as an etching mask for vacuum-compatible photolithography. 相似文献
2.
R. N. Jacobs E. W. Robinson M. Jaime-Vasquez A. J. Stoltz J. Markunas L. A. Almeida P. R. Boyd J. H. Dinan L. Salamanca-Riba 《Journal of Electronic Materials》2006,35(6):1474-1480
A vacuum-compatible process for carrying out lithography on Hg1−xCdxTe and CdTe films was previously demonstrated. It was shown that hydrogenated amorphous silicon (a-Si:H) could be used as
a dry resist by projecting a pattern onto its surface using excimer laser irradiation and then developing that pattern by
hydrogen plasma etching. Pattern transfer to an underlying Hg1−xCdxTe film was then carried out via Ar/H2 plasma etching in an electron cyclotron resonance (ECR) reactor. Despite the successful demonstration of pattern transfer,
the possibility of inducing harmful effects in the Hg1−xCdxTe film due to this vacuum lithography procedure had not been explored. Here we present structural and surface compositional
analyses of Hg1−xCdxTe films at key stages of the a-Si:H vacuum lithography procedure. X-ray diffraction double crystal rocking curves taken before
and after a-Si:H deposition and after development etching were identical, indicating that bulk structural changes in the Hg1−xCdxTe film are not induced by these processes. Cross-section transmission electron microscopy studies show that laser-induced
heating in the 350 nm thick a-Si:H overlayer is not sufficient to cause structural damage in the underlying Hg1−xCdxTe surface. In vacuo surface analysis via Auger electron spectroscopy and ion scattering spectroscopy suggest that the hydrogen
plasma development process produces Hg-deficient surfaces but does not introduce C contamination. However, after ECR plasma
etching into the Hg1−xCdxTe film, the measured x value is much closer to that of the bulk. 相似文献
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5.
We have used transmission electron microscopy to study the [100] and [010] dark line defects (DLDs) produced after photodegradation
of a ZnSSe-based/GaAs heterostructure. Our results show that the DLDs are networks of elongated dislocation loops or half-loops
that originate in the quantum well region during device operation. Our results also show that after photodegradation the grownin
or pre-existing Frank-type stacking faults become tangles of dislocations. In contrast, the Shockley-type stacking faults
remained unchanged for the photodegradation conditions studied indicating that they are more resistant to photodegradation
than the Frank-type stacking faults. Our results suggest that the Frank-type stacking faults are the sources of the DLDs.
The mechanism for degradation probably starts by the emission of very small clusters of vacancies from the Frank-type faults.
Upon further illumination the dislocation loops bounding the vacancies grow by gliding on {111} planes and become hairpin-like
dislocation loops. 相似文献
6.
Wendy L. Sarney L. Salamanca-Riba R. D. Vispute P. Zhou C. Taylor M. G. Spencer K. A. Jones 《Journal of Electronic Materials》2000,29(3):359-363
Due to large lattice and thermal expansion coefficient mismatches, SiC films grown on Si are usually low quality. To provide
a more stable growth front we added Ge in the form of GeH4 to the reactant gases in a MOCVD reactor. Several SiC films with Ge flow rates ranging from 0–50 sccm were grown on (111)
Si substrates at 1000°C. TEM results show that the crystalline quality is amorphous or polycrystalline for Ge flow rates at
or below 15 sccm. Samples grown at Ge flow rates at or exceeding 20 sccm have an initial layer of single crystalline 3C SiC
followed by heavily twinned crystalline 3C SiC. In particular, the samples grown with 20–30 sccm Ge contain an 80 nm initial
layer of reasonably high quality single crystal 3C SiC. 相似文献
7.
On the origin of high-temperature ferromagnetism in the low-temperature-processed Mn-Zn-O system 总被引:3,自引:0,他引:3
Kundaliya DC Ogale SB Lofland SE Dhar S Metting CJ Shinde SR Ma Z Varughese B Ramanujachary KV Salamanca-Riba L Venkatesan T 《Nature materials》2004,3(10):709-714
The recent discovery of ferromagnetism above room temperature in low-temperature-processed MnO(2)-ZnO has generated significant interest. Using suitably designed bulk and thin-film studies, we demonstrate that the ferromagnetism in this system originates in a metastable phase rather than by carrier-induced interaction between separated Mn atoms in ZnO. The ferromagnetism persists up to approximately 980 K, and further heating transforms the metastable phase and kills the ferromagnetism. By studying the interface diffusion and reaction between thin-film bilayers of Mn and Zn oxides, we show that a uniform solution of Mn in ZnO does not form under low-temperature processing. Instead, a metastable ferromagnetic phase develops by Zn diffusion into the Mn oxide. Direct low-temperature film growth of Zn-incorporated Mn oxide by pulsed laser deposition shows ferromagnetism at low Zn concentration for an optimum oxygen growth pressure. Our results strongly suggest that the observed ferromagnetic phase is oxygen-vacancy-stabilized Mn(2-x)Zn(x)O(3-delta.). 相似文献
8.
C. D. Lee V. Ramachandran A. Sagar R. M. Feenstra D. W. Greve W. L. Sarney L. Salamanca-Riba D. C. Look Song Bai W. J. Choyke R. P. Devaty 《Journal of Electronic Materials》2001,30(3):162-169
The structural, electrical, and optical properties of GaN grown on 6H-SiC(0001) substrates by molecular beam epitaxy are studied.
Suitable substrate preparation and growth conditions are found to greatly improve the structural quality of the films. Threading
dislocation densities of about 3×109 cm−2 for edge dislocations and <1×106 cm−2 for screw dislocations are achieved in GaN films of 0.8 μm thickness. Mechanisms of dislocation generation and annihilation
are discussed. Increasing the Ga to N flux ratio used during growth is found to improve the surface morphology. An unintentional
electron concentration in the films of about 5×1017 cm−3 is observed, and is attributed to excess Si in the films due to a Si-cleaning step used in the substrate preparation. Results
from optical characterization are correlated with the structural and electronic studies. 相似文献
9.
L. H. Kuo L. Salamanca-Riba J. M. Depuydt H. Chèng J. Qiu 《Journal of Electronic Materials》1994,23(3):275-281
Nitrogen doped ZnSe/GaAs heterostructures grown at 150 and 250°C were studied by transmission électron microscopy (TEM). The
density of threading dislocations and the interfacial dislocation structure in ZnSe/GaAs heterostructures are related to the
N-doping concentration. In addition, in-situ TEM heating studies show that Frank partial dislocations formed below critical
thickness in N-doped ZnSe/GaAs are the sources for nucleation of a regular array of misfit dislocations at the ZnSe/GaAs interface.
By the dissociation of the Frank partial dislocations and interaction reactions between the dislocations, the 60° misfit dislocations
form. The Frank partial dislocations bound stacking faults which usually form in pairs at the film/substrate interface. The
density of stacking faults increases with increasing N-doping concentration. Thus, at high N-doping levels, the dislocation
nucleation sources are close together and not all of the Frank partial dislocations dissociate, so that a high density of
threading dislocations results in samples with high N-doping concentrations. The high density of threading dislocations in
the ZnSe film are found to be associated with a reduction or saturation of the net carrier density. 相似文献
10.
A. K. Ballal L. Salamanca-Riba D. L. Partin J. Heremans L. Green B. K. Fuller 《Journal of Electronic Materials》1993,22(4):383-389
In this work, we investigate the role of a low temperature nucleation layer on the interfacial properties of InAs epilayers
grown on (100) semi-insulating InP substrates using a two-step metalorganic chemical vapor deposition method. Cross-sectional
and plan-view transmission electron microscopy studies were carried out on InAs films of nearly equal total film thicknesses
but for different thicknesses of a nucleation layer of InAs deposited at low temperature on the substrate. Our studies show
that thermal etchpits are created at the interface between the InAs film, and the InP substrate for thin nucleation layer
thicknesses. This is because the low temperature nucleation layer of InAs does not cover completely the surface of the InP
substrate. Hence, when the temperature is raised to deposit the bulk of the InAs film, severe thermal pitting is observed
at the interface. These thermal etchpits are sources of threading dislocations. To obtain high quality InAs films and suppress
interfacial pitting there is an optimum thickness of the nucleation layer. Also, our studies show that there is a relationship
between the density of defects in the film and the thickness of the nucleation layer. This in turn relates to the variation
of the electronic properties of the InAs films. We have observed that for all nucleation layer thicknesses, the density of
threading dislocations is higher close to the interface than at the free surface of the film. 相似文献