In-situ Measurement of GaAs Optical Constants and Surface Quality, as Functions of Temperature

1991 ◽  
Vol 222 ◽  
Author(s):  
Huade Yao ◽  
Paul G. Snyder
Keyword(s):  
Room Temperature ◽  
Optical Constants ◽  
Molecular Beam ◽  
Elevated Temperatures ◽  
Native Oxide ◽  
Time Data ◽  
Gaas Sample ◽  
Optical Thermometer ◽  
Surface Changes

ABSTRACTIn-situ spectroscopic ellipsometry (SE) was applied to monitor GaAs (100) surface changes induced at elevated temperatures inside an ultrahigh vacuum (UHV) chamber (<1×10−9 torr base pressure, without As overpressure). The real time data showed clearly the evolution of the native-oxide desorption at ∼577°C, on a molecular-beam-epitaxy (MBE)-grown GaAs (100) surface. In addition, surface degradation was found before and after the oxide desorption. A clean and smooth surface was obtained from an arsenic-capped, MBE-grown GaAs sample, after the arsenic coating was evaporated at ∼350 °C inside the UHV. Pseudodielectric functions <ε>GaAs, from 1.6 eV to 4.5 eV, were obtained through the SE measurements, from this oxide-free surface, at temperatures ranging from room temperature (RT) to ∼610 °C. These <ε> data were used as reference data to develop an algorithm for determining surface temperatures from in-situ SE measurements, thus turning the SE instrument into a sensitive optical thermometer.

GaAs(100) Surface Modifications at Elevated Temperatures, Studied By In-Situ Spectroscopic Ellipsometry

1990 ◽  
Vol 202 ◽  
Author(s):  
Huade Yao ◽  
Paul G Snyder ◽  
John A Woollam
Keyword(s):  
Spectroscopic Ellipsometry ◽  
Room Temperature ◽  
Molecular Beam ◽  
Elevated Temperatures ◽  
Surface Region ◽  
Gaas Surface ◽  
Near Surface ◽  
Before And After ◽  
Surface Changes

ABSTRACTSpectroscopic ellipsometric (SE) measurements of GaAs (100) were carried out in an ultrahigh vacuum (UHV) chamber, without arsenic overpressure, at temperatures ranging from room temperature (RT) to ∼610°C. Surface changes induced at elevated temperatures were monitored by in-situ spectroscopic ellipsometry. The SE data clearly displayed in real time the process of desorption of the GaAs-surface-oxide overlayer at ∼580°C. In addition, changes in the near-surface region were observed before and after the oxide desorption. The near-subsurface region (top 50–100 Å) became less optically dense after being heated to 540°C or higher. For comparison, a pre-arsenic-capped molecular-beam-epitaxy (MBE)-grown GaAs surface was also studied. After the arsenic cap was evaporated off at ∼350°C, this surface remained smooth and clean as it was heated to higher temperatures.

Temperature Dependence of Optical Properties of AlAs, Studied by In Situ Spectroscopic Ellipsometry

1992 ◽  
Vol 242 ◽  
Author(s):  
Huade Yao ◽  
Paul G. Snyder ◽  
Kathleen Stair ◽  
Thomas Bird
Keyword(s):  
Optical Properties ◽  
Molecular Beam Epitaxy ◽  
Room Temperature ◽  
Optical Constants ◽  
Molecular Beam ◽  
Gaas Layer ◽  
Temperature Dependent ◽  
Harmonic Oscillator Approximation ◽  
Quantitative Analyses

ABSTRACTThe dielectric functions ε = ε1+iε2 of AlAs were determined from 1.5 eV to 5.0 eV, by spectroscopie ellipsometry (SE), from room temperature (RT) to ∼577 °C in an ultrahigh vacuum (UHV) chamber. Molecular beam epitaxy (MBE)-grown AlAs was covered by a thin GaAs layer, which was passivated by arsenic capping to prevent oxidation. The arsenic cap was desorbed inside the UHV chamber. SE measurements of the unoxidized sample were made, at various temperatures. Temperature dependent optical constants of AlAs were obtained by mathematically removing the effects of the GaAs cap and substrate. Quantitative analyses of the variations of critical-point energies with temperature, by using the harmonic oscillator approximation (HOA), indicate that the E1 and E1+Δ1 energies decrease -350 meV as temperature increases from RT to 500 °C.

Oxide Scale Formation on Iron-Chromium Alloys in Elevated Temperature Air Environments

CORROSION ◽  
1981 ◽  
Vol 37 (12) ◽  
pp. 700-711 ◽  
Author(s):  
P. Fabis ◽  
R. Heidersbach ◽  
C. Brown ◽  
T. Rockett
Keyword(s):  
Raman Spectroscopy ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Experimental Program ◽  
Oxide Scales ◽  
Chromium Alloys ◽  
Spectroscopy Instrumentation ◽  
Commercial Iron ◽  
Iron Chromium

Abstract Oxide scales formed on metals at elevated temperatures may be different, both chemically and structurally, from the scales on the metal once it has cooled to room temperature. This paper discusses Raman spectroscopy instrumentation for the in-situ identification of scales formed on metal surfaces exposed to gaseous environments. The results of an experimental program to characterize scales formed on two commercial iron-chromium alloys, AISI 446 and 502, in air and oxygen environments are also presented.

Laser Processing in Silicon Molecular Beam Epitaxy

1981 ◽  
Vol 4 ◽  
Author(s):  
T. De Jong ◽  
L. Smit ◽  
V.V. Korablev ◽  
F.W. Saris
Keyword(s):  
Molecular Beam Epitaxy ◽  
Laser Processing ◽  
Room Temperature ◽  
Molecular Beam ◽  
Pulsed Laser ◽  
Epitaxial Layers ◽  
Epitaxial Silicon ◽  
Temperature Deposition ◽  
Substrate Surfaces

ABSTRACTWe have grown epitaxial silicon films on silicon (100), (110) and (111) oriented substrates, using pulsed ruby laser irradiation as a means to obtain clean, ordered substrate surfaces. On these surfaces epitaxial layers were grown in two ways: I. Rȯom temperature deposition and pulsed laser induced epitaxy of 100–300 nm films was carried out repeatedly, yielding ∼1 μm thick epitaxial layers. II. Low temperature molecular beam epitaxy (M.B.E.), even at 250°C on Si(100),of layers up to 1 μm.Applying the second technique to implanted substrates, we annealed and cleaned arsenic implanted silicon (100) samples in situ, and produced epitaxial overlayers of 100–1000 nm, thus creating a buried n-type channel in silicon.

Electron microscope studies of climb of dissociated dislocations

1978 ◽  
Vol 36 (1) ◽  
pp. 324-325
Author(s):  
C.B. Carter ◽  
D. Cherns ◽  
P.B. Hirsch ◽  
H. Saka
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Point Defects ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Al Alloys ◽  
Weak Beam ◽  
High Supersaturation ◽  
Beam Technique

The mechanism of climb of dissociated dislocations in f.c.c. metals and alloys is not well understood. Climb of dislocations by absorption or emission of vacancies at existing jogs in dissociated dislocations has been observed using the “weak-beam” technique of electron microscopy, but the mechanism of nucleation of jogs is not clear. In this paper we report some results of experiments designed to study the nucleation problem, and more generally the mechanism of absorption of point defects under conditions of high supersaturation.Thin (111) sections of deformed single crystals of Cu-Al alloys, of various compositions, have been electron irradiated in an AEI EM7 HVEM up to 1 MeV, either at room temperature, or elevated temperatures up to 200°C, using a goniometer heating stage. Observations under weak beam conditions have been made a) in situ in the HVEM b) at 100kV in an JEM100B, following irradiation in the HVEM. Interstitials produced by the irradiation are expected to be preferentially attracted to the dislocations because of the strong dislocation-interstitial interaction.

Islanding and Surface Diffusion in Semiconductor Heteroepitaxy: Ge on Si

1987 ◽  
Vol 102 ◽  
Author(s):  
G. J. Fisanick ◽  
H.-J. Gossmann ◽  
P. Kuo
Keyword(s):  
Surface Diffusion ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Size Distributions ◽  
Beam Irradiation ◽  
Island Size ◽  
Uniform Growth ◽  
Extensive Surface

ABSTRACTIslanding and surface diffusion for Ge on Si(111)7×7 and Si(100)2×1 surfaces were examined in a UHV apparatus with in situ scanning Auger/SEM capabilities. At room-temperature uniform growth is observed, while elevated temperatures lead to Stranski-Krastanov growth with complex island size distributions. Extensive surface diffusion is observed on Si(100)2×l; however, surface diffusion is demonstrated to be extremely sensitive to contamination with carbon on the order of ≈0.05 ML, as well as to e-beam irradiation.

Controlled Growth and Characterization of Non-tapered InN Nanowires on Si(111) Substrates by Molecular Beam Epitaxy

2009 ◽  
Vol 1178 ◽  
Author(s):  
Yi-Lu Chang ◽  
Arya Fatehi ◽  
Feng Li ◽  
Zetian Mi
Keyword(s):  
Molecular Beam Epitaxy ◽  
Epitaxial Growth ◽  
Room Temperature ◽  
Molecular Beam ◽  
Stacking Faults ◽  
Seeding Layer ◽  
Mbe Growth ◽  
Molecular Beam Epitaxial

AbstractWe have performed a detailed investigation of the molecular beam epitaxial (MBE) growth and characterization of InN nanowires spontaneously formed on Si(111) substrates under nitrogen rich conditions. Controlled epitaxial growth of InN nanowires (NWs) has been demonstrated by using an in situ deposited thin (˜ 0.5 nm) In seeding layer prior to the initiation of growth. By applying this technique, we have achieved non-tapered epitaxial InN NWs that are relatively free of dislocations and stacking faults. Such InN NW ensembles display strong photoluminescence (PL) at room temperature and considerably reduced spectral broadening, with very narrow spectral linewidths of 22 and 40 meV at 77 K and 300 K, respectively.

Microstructures and Mechanical Properties of NiAl+Mo In-Situ Eutectic Composites

1990 ◽  
Vol 194 ◽  
Author(s):  
P. R. Subramanian ◽  
M. G. Mendiratta ◽  
D. B. Miracle ◽  
D. M. Dimiduk
Keyword(s):  
Mechanical Properties ◽  
Solid Solution ◽  
Room Temperature ◽  
Composite System ◽  
Elevated Temperatures ◽  
Two Phase ◽  
Structural Applications ◽  
Temperature Fracture

AbstractThe quasibinary NiAI-Mo system exhibits a large two-phase field between NiAl and the terminal (Mo) solid solution, and offers the potential for producing in-situ eutectic composites for high-temperature structural applications. The phase stability of this composite system was experimentally evaluated, following long-term exposures at elevated temperatures. Bend strengths as a function of temperature and room-temperature fracture toughness data are presented for selected NiA1-Mo alloys, together with results from fractography observations.

Rapid Evaluation of Thin Film Interfacial Reactions Using Temperature-Ramped Measurements

1993 ◽  
Vol 318 ◽  
Author(s):  
J.M.E. Harper ◽  
L.A. Clevenger ◽  
E.G. Colgan ◽  
C. Cabral ◽  
B. Arcot
Keyword(s):  
Thin Film ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Interfacial Reactions ◽  
Rapid Evaluation ◽  
Cu Alloys ◽  
Thermal Measurements ◽  
Cu Dissolution ◽  
Interfacial Oxygen

ABSTRACTWe describe an approach for rapid evaluation of thin film interfacial reactions using a combination of temperature-ramped in situ measurements of sheet resistance, calorimetry and stress. Electrical, mechanical and thermal measurements at elevated temperatures provide detailed reaction information which is unavailable in room temperature measurements. Kinetic data is particularly useful in making comparisons with mechanistic models. The following examples are discussed:1. Effects of interfacial oxygen on Ta as a diffusion barrier between Cu and Si,2. Effects of interfacial oxygen on the Cu/Mg reaction to form CuMg2 and Cu2Mg,3. Effects of the density of internal interfaces (grain boundaries) on Al2Cu dissolution and precipitation in Al-Cu alloys.

Temperature Dependence of Nanoscale Friction Investigated with Thermal AFM Probes

2009 ◽  
Vol 1226 ◽  
Author(s):  
Christian Greiner ◽  
Jonathan R. Felts ◽  
Zhenting Dai ◽  
William P. King ◽  
Robert W. Carpick
Keyword(s):  
Room Temperature ◽  
Capillary Condensation ◽  
Constant Load ◽  
Native Oxide ◽  
Silicon Substrates ◽  
Ambient Atmosphere ◽  
Ambient Conditions ◽  
Nanoscale Friction ◽  
Kinetics Of

AbstractMeasurements of nanoscale friction between silicon AFM tips featuring an in-situ solid state heater and silicon substrates (both with native oxide) were performed. The temperature of the heater was varied between room temperature and approximately 650 °C. For these temperatures and the silicon substrate, the temperatures at the point of contact are estimated to range from room temperature to approximately 120±20 °C. Experiments were carried out in ambient atmosphere (˜30% relative humidity) and under dry nitrogen. Tests under constant load revealed that in the presence of ambient, friction increased with heater temperature whereas it did not change in dry nitrogen. For experiments carried out for different tip velocities (40 to 7800 nm/s), friction decreased with velocity in ambient and did not change in dry nitrogen. Both trends can be explained by thermally-assisted formation of capillary bridges between tip and substrate and the kinetics of capillary condensation under ambient conditions.

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