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.

Coalescence between Au nanoparticles as induced by nanocurvature effect and electron beam athermal activation effect

Nanoscale ◽  
2018 ◽  
Vol 10 (17) ◽  
pp. 7978-7983 ◽  
Author(s):  
Liang Cheng ◽  
Xianfang Zhu ◽  
Jiangbin Su
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Room Temperature ◽  
Electron Beam Irradiation ◽  
Au Nanoparticles ◽  
Beam Irradiation ◽  
Activation Effect ◽  
Transmission Electron

The coalescence of two single-crystalline Au nanoparticles on surface of amorphous SiOxnanowire, as induced by electron beam irradiation, wasin situstudied at room temperature in a transmission electron microscope.

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.

Heteroepitaxy of Ge on Vicinal Si(100)

1990 ◽  
Vol 198 ◽  
Author(s):  
Mohan Krishnamurthy ◽  
Jeff S. Drucker ◽  
J.A. Venables
Keyword(s):  
Intermediate Layer ◽  
Room Temperature ◽  
Secondary Electron ◽  
Elevated Temperatures ◽  
Film Growth ◽  
Growth Parameters ◽  
Ex Situ ◽  
Nucleation Density ◽  
Size Distributions ◽  
Surface Steps

ABSTRACTThe initial stages of germanium heteroepitaxy on vicinal Si(100) have been studied using in-situ deposition in a UHV STEM. Germanium was deposited using molecular beam techniques onto substrates misoriented 1° and 5* toward <110> held at room temperature, 375°C and 525°C. Film thicknesses were in the range 4-6 ML, just greater than the stable intermediate layer of 3-4ML (1ML = 0.14nm). The Ge clusters were observed using biassed secondary electron (b-SE) imaging with nanometer resolution. Comparisons were made between deposition at the elevated temperatures, and room temperature deposition followed by anneals at the same temperatures.Annealing the low temperature deposits produces coarsening of the islands which is similar on the 1° and 5° samples. Island size distributions and other film growth parameters obtained from the 375°C and 525°C anneals indicate that the coarsening is different at these temperatures and is possibly affected by instabilities in the intermediate layer. Results of the high temperature depositions indicate that neither surface steps nor the edges of islands act as perfect sinks, and that diffusion distances are of the order of several microns. The nucleation density and size distributions are markedly different for deposition at 375°C and 525°C possibly due to competitive capture at strong sinks.In a parallel set of experiments in a standard UHV chamber, macroscopic wafer samples were analyzed with RHEED, Auger and secondary electron spectroscopy. These correlate well with the intermediate layer thicknesses previously reported in the literature, and the large contrast observed in the b-SE images. Ex situ TEM studies of samples grown in this chamber show islands with various contrast features including those of coherent strain.

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.

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.

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.

Effects of NaBH4 Additions on Hydrogen Absorption by Nanostructured FeTi Powders

2008 ◽  
Vol 587-588 ◽  
pp. 921-925 ◽  
Author(s):  
Sofia F. Marques ◽  
Raquel A. Silva ◽  
Jose Brito Correia ◽  
Nobumitsu Shohoji ◽  
Carmen M. Rangel
Keyword(s):  
Hydrogen Absorption ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Low Cost ◽  
Reaction Products ◽  
X Ray Diffraction ◽  
X Ray ◽  
Gas Atmosphere ◽  
Scanning Electron

FeTi intermetallic powders are very promising media for reversible hydrogen storage. However, difficult activation treatments including annealing at elevated temperatures in high pressure H2 gas atmosphere are mandatory. In the present work nanostructured FeTi powders were produced and activated in situ at room temperature using mechanical alloying/milling (MA/MM) of pure metallic constituents, Fe and Ti, added with sodium borohydride. The resultant powders, FeTiHx, already H2 pre-charged, absorbed a significant amount of H2 but require optimization for reversible absorption/desorption. This system has one of the highest volumetric storage capacities and can be produced at low cost. Several parameters of the as-milled powders were controlled. The phase constitution of the reaction products was characterized by X-ray diffraction and scanning electron microscopy and the absorption isotherms of the activated powders were determined.

In situ solid-state NMR studies of Ca3SiO5: hydration at room temperature and at elevated temperatures using 29Si enrichment

1994 ◽  
Vol 29 (15) ◽  
pp. 3926-3940 ◽  
Author(s):  
A. R. Brough ◽  
C. M. Dobson ◽  
I. G. Richardson ◽  
G. W. Groves
Keyword(s):  
Solid State ◽  
Solid State Nmr ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Nmr Studies
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