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.

Studies of Ge/Si(100) and Observation of Atomic Steps on Si(100) using Biassed Secondary Electron Imaging in a UHV STEM

1990 ◽  
Vol 48 (1) ◽  
pp. 308-309
Author(s):  
Mohan Krishnamurthy ◽  
Jeff S. Drucker ◽  
John A. Venablest
Keyword(s):  
Secondary Electron ◽  
Critical Thickness ◽  
Surface Defects ◽  
Film Growth ◽  
Growth Parameters ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Surface Steps ◽  
Epitaxial Crystal Growth ◽  
Electron Imaging

Secondary Electron Imaging (SEI) has become a useful mode of studying surfaces in SEM[1] and STEM[2,3] instruments. Samples have been biassed (b-SEI) to provide increased sensitivity to topographic and thin film deposits in ultra high vacuum (UHV)-SEM[1,4]; but this has not generally been done in previous STEM studies. The recently developed UHV-STEM ( codenamed MIDAS) at ASU has efficient collection of secondary electrons using a 'parallelizer' and full sample preparation system[5]. Here we report in-situ deposition and annealing studies on the Ge/Si(100) epitaxial system, and the observation of surface steps on vicinal Si(100) using b-SEI under UHV conditions in MIDAS.Epitaxial crystal growth has previously been studied using SEM and SAM based experiments [4]. The influence of surface defects such as steps on epitaxial growth requires study with high spatial resolution, which we report for the Ge/Si(100) system. Ge grows on Si(100) in the Stranski-Krastonov growth mode wherein it forms pseudomorphic layers for the first 3-4 ML (critical thickness) and beyond which it clusters into islands[6]. In the present experiment, Ge was deposited onto clean Si(100) substrates misoriented 1° and 5° toward <110>. This was done using a mini MBE Knudsen cell at base pressure ~ 5×10-11 mbar and at typical rates of 0.1ML/min (1ML =0.14nm). Depositions just above the critical thickness were done for substrates kept at room temperature, 375°C and 525°C. The R T deposits were annealed at 375°C and 525°C for various times. Detailed studies were done of the initial stages of clustering into very fine (∼1nm) Ge islands and their subsequent coarsening and facetting with longer anneals. From the particle size distributions as a function of time and temperature, useful film growth parameters have been obtained. Fig. 1 shows a b-SE image of Ge island size distribution for a R T deposit and anneal at 525°C. Fig.2(a) shows the distribution for a deposition at 375°C and Fig.2(b) shows at a higher magnification a large facetted island of Ge. Fig.3 shows a distribution of very fine islands from a 525°C deposition. A strong contrast is obtained from these islands which are at most a few ML thick and mottled structure can be seen in the background between the islands, especially in Fig.2(a) and Fig.3.

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.

Self Assembly of Anisotropic Organic Molecules: Diffusion versus Sticking Anisotropy

2005 ◽  
Vol 901 ◽  
Author(s):  
Stephen Berkebile ◽  
Georg Koller ◽  
Gregor Hlawacek ◽  
Martin Oehzelt ◽  
Roland Resel ◽  
...  
Keyword(s):  
Growth Kinetics ◽  
Self Assembly ◽  
Molecular Orientation ◽  
Elevated Temperatures ◽  
Film Growth ◽  
Building Blocks ◽  
Molecular Structures ◽  
Ex Situ ◽  
Diffusion Anisotropy ◽  
X Ray

AbstractThe molecular/crystal orientation and morphology of active molecular structures is a key determinant for the function of nanoscaled organic devices. In π-conjugated systems, both charge transport and optical properties will strongly depend on the molecular orientation due to the highly anisotropic charge carrier mobility in these organic crystals and the anisotropic absorption and luminescence behavior of the molecules. Although the importance of organic on inorganic interface formation and thin film growth is widely acknowledged, little is known regarding the growth kinetics. A better understanding of the processes driving molecular self-assembly is necessary if the self-assembly process is to be controlled. Moreover, it is interesting as the anisotropy of the molecular building blocks presents a fundamental difference from what is known from inorganic growth. Here we show that either sticking or diffusion anisotropy can control the growth depending on preparation conditions. This is illustrated by an investigation into the growth of sexiphenyl (6P) on the anisotropic TiO2(110)-(1×1) surface for temperatures between 80K and 400K using in-situ UHV photoemission, x-ray absorption spectroscopy, synchrotron x-ray diffraction and ex-situ atomic force microscopy. For 6P adsorption even at 80K we found that the molecules orient parallel to the TiO2 oxygen rows and form small crystallites. At 300K this molecular orientation is retained and large micrometer sized 6P(203) oriented needles running perpendicular to oxygen substrate rows are formed. In contrast, for growth at elevated temperatures the 6P molecular axis is near perpendicular to the surface and large islands elongated parallel to the substrate rows are formed. These differences in crystallite orientation and morphology can be explained by the domination of the growth kinetics by either sticking or diffusion anisotropy depending on growth temperature.

Room Temperature Growth of Silicon Dioxide Using a Low Energy Ion Beam

1986 ◽  
Vol 75 ◽  
Author(s):  
S. S. Todorov ◽  
E. R. Fossum
Keyword(s):  
Silicon Dioxide ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Film Growth ◽  
Ion Beam ◽  
Silicon Surfaces ◽  
Ion Energy ◽  
Thermally Driven ◽  
Thin Oxide Films ◽  
Substrate Temperatures

AbstractUltra-thin films of silicon dioxide are formed on silicon surfaces at room temperature by direct bombardment with an oxygen-containing ion beam at energies of 150 eV or less. The process of film growth is studied.through ellipsometric measurements of their properties as a function of ion energy and dose, oxygen partial pressure and substrate temperature. Typical oxide thicknesses of the order of 50 Å are obtained by three minute or longer exposures to beams of current density 135 μA/cm2. Ion-beam grown oxides are compared to conventional thin oxide films grown at elevated temperatures and show the same stoichiometry. The growth rate decreases rapidly after a continuous oxide film has been formed. Performing the ion bombardment at elevated substrate temperatures leads to only small enhancement of the oxide growth indicating non-thermally driven reaction kinetics.

scholarly journals Impact of Tungsten Incorporation on the Tribomechanical Behavior of AlCrWxSiN Films at Room and Elevated Temperature

Coatings ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1033
Author(s):  
Wolfgang Tillmann ◽  
Alexander Fehr ◽  
Dominic Stangier
Keyword(s):  
Magnetron Sputtering ◽  
Coefficient Of Friction ◽  
Friction And Wear ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Film Growth ◽  
Wear Behavior ◽  
Friction Reduction ◽  
Wear Coefficient ◽  
The Coefficient Of Friction

AlCrWxSiN thin films (0 ≤ x ≤ 17.1 at.%) were synthesized by means of a hybrid magnetron sputtering process, merging direct current (DC) as well as tungsten high power impulse magnetron sputtering (HiPIMS) supplies. The influences of increasing the tungsten contents on the structural as well as the friction and wear behavior at room and high temperatures (500 °C) were elaborated. As a reference, a W61.4N38.6 system served to analyze synergetic effects on the oxidation behavior. Increased tungsten contents in AlCrWxSiN resulted in more distinctive (200)-, (202)-, and (311)- crystal orientations. A W/Cr ratio of ~1 could be correlated with a denser film growth, the highest hardness (24.3 ± 0.7 GPa), and a significantly decreased wear coefficient (<0.3 × 10−5 mm3/Nm). Tribological tests performed at room temperature revealed that the coefficient of friction decreased with higher tungsten contents to µ~0.35. In contrast, at elevated temperatures, the coefficient of friction increased with higher W concentrations due to spotty oxidations in the wear track, which resulted in a locally increased surface roughness. Finally, a phase transformation of the WN film to m-WO3 did not contribute to a friction reduction at 500 °C.

Formation of Nickel Ferrite Films by Solid-State Reaction

1997 ◽  
Vol 3 (S2) ◽  
pp. 739-740
Author(s):  
Matthew T. Johnson ◽  
Paul G. Kotula ◽  
C. Barry Carter
Keyword(s):  
Thin Films ◽  
Solid State ◽  
Solid State Reaction ◽  
Nickel Ferrite ◽  
Elevated Temperatures ◽  
Film Growth ◽  
Ex Situ ◽  
First Case ◽  
Morphological Differences

Nickel ferrite (NiFe2O4) thin films are of potential interest for magnetic applications. In the present study, the production of NiFe2O4 by solid-state reaction between thin films of hematite (α-Fe2O3) and nickel oxide (NiO) on (0001) sapphire (α-Fe2O3) substrates has been examined. The NiFe2O4 thin films were prepared by two different methods. In the first case the NiFe2O4film was grown in situ in the deposition system, while in the second case the NiFe2O4 film was formed ex situ by reacting at elevated temperatures in air. These two methods of reaction lead to interesting morphological differences in the ferrite layers.Epilayers of α-Fe2O3 followed by NiO were deposited onto (0001) α-Al2O3 by pulsed-laser deposition (PLD) in 6 mTorr O2. NiFe2O4 films were obtained by reacting the starting films in two different ways: in situ (during film growth) and ex situ.. In both cases, the α-Fe2O3 films were grown under the same conditions while those for the deposition of the NiO layers were different.

In Situ Characterization of Ain Films Grown on Silicon by MOCVD

1998 ◽  
Vol 512 ◽  
Author(s):  
A. D. Serra ◽  
H. H. Richardson
Keyword(s):  
Film Growth ◽  
Growth Parameters ◽  
Emission Spectra ◽  
Ex Situ ◽  
X Ray Diffraction ◽  
In Situ Characterization ◽  
X Ray ◽  
Ir Emission

ABSTRACTFilms of AIN were grown on Si under vacuum pressure at 900°C and examined ex situ with infrared reflectance spectroscopy and microscopy, scanning electron microscopy, x-ray diffraction and rutherford backscattering spectroscopy. Collection of IR emission spectra for in situ characterization was successful and used to identify growth parameters during film growth.

In Situ Ellipsometry Study of the Diamond Film Evolution Process

1999 ◽  
Vol 580 ◽  
Author(s):  
L.M. Cancel ◽  
O.L. Figueroa ◽  
B.R. Weiner ◽  
G. Morell
Keyword(s):  
Chemical Vapor Deposition ◽  
Diamond Film ◽  
Vapor Deposition ◽  
Film Growth ◽  
Growth Parameters ◽  
Chemical Vapor ◽  
Deposition Process ◽  
Ex Situ ◽  
Film Microstructure

AbstractWe employed in situ ellipsometry to monitor and study the nucleation and growth processes of diamond thin films fabricated by chemical vapor deposition. The films were grown on Si substrates in a hot filament chemical vapor deposition (HFCVD) system. We monitored the effective extinction coefficient (k) at 1.96 eV of the diamond films during growth through ellipsometry. The behavior of this parameter was found to be reproducible, making it suitable as a basis for dividing the deposition process into intervals. The film growth was aborted at various k values yielding diamond film samples that represent snapshots of the growth process at different stages. These films were removed for ex situ characterization using Raman spectroscopy and scanning electron microscopy (SEM). These characterizations were used to correlate the ellipsometric data with film microstructure, enabling us from now on to monitor the diamond film growth in real time and to design experiments targeted at modifying the film microstructure by changing growth parameters in the middle of film fabrication.

Scanning Electron Microscopy-cuticular Lesions on the Roundworm Ascaris Suum

1970 ◽  
Vol 28 ◽  
pp. 114-115
Author(s):  
P. A. Madden ◽  
W. R. Anderson
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Freeze Drying ◽  
Room Temperature ◽  
Secondary Electron ◽  
Distilled Water ◽  
Freeze Dried ◽  
Silver Paint ◽  
To Come ◽  
Scanning Electron

The intestinal roundworm of swine is pinkish in color and about the diameter of a lead pencil. Adult worms, taken from parasitized swine, frequently were observed with macroscopic lesions on their cuticule. Those possessing such lesions were rinsed in distilled water, and cylindrical segments of the affected areas were removed. Some of the segments were fixed in buffered formalin before freeze-drying; others were freeze-dried immediately. Initially, specimens were quenched in liquid freon followed by immersion in liquid nitrogen. They were then placed in ampuoles in a freezer at −45C and sublimated by vacuum until dry. After the specimens appeared dry, the freezer was allowed to come to room temperature slowly while the vacuum was maintained. The dried specimens were attached to metal pegs with conductive silver paint and placed in a vacuum evaporator on a rotating tilting stage. They were then coated by evaporating an alloy of 20% palladium and 80% gold to a thickness of approximately 300 A°. The specimens were examined by secondary electron emmission in a scanning electron microscope.

Mechanical Properties and Dislocation Structure of Single Crystal Cdte Deformed in Compression at 300°C

1976 ◽  
Vol 34 ◽  
pp. 592-593
Author(s):  
Ernest L. Hall ◽  
J. B. Vander Sande
Keyword(s):  
Mechanical Properties ◽  
Single Crystal ◽  
Dislocation Structure ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Strain Curve ◽  
Optical Devices ◽  
Semiconductor Compound ◽  
Wide Range ◽  
Sample Orientation

The present paper describes research on the mechanical properties and related dislocation structure of CdTe, a II-VI semiconductor compound with a wide range of uses in electrical and optical devices. At room temperature CdTe exhibits little plasticity and at the same time relatively low strength and hardness. The mechanical behavior of CdTe was examined at elevated temperatures with the goal of understanding plastic flow in this material and eventually improving the room temperature properties. Several samples of single crystal CdTe of identical size and crystallographic orientation were deformed in compression at 300°C to various levels of total strain. A resolved shear stress vs. compressive glide strain curve (Figure la) was derived from the results of the tests and the knowledge of the sample orientation.

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