Critical thickness for plastic relaxation of SiGe on Si(001) revisited

2011 ◽  
Vol 110 (8) ◽  
pp. 083529 ◽  
Author(s):  
J. M. Hartmann ◽  
A. Abbadie ◽  
S. Favier
Keyword(s):  
Critical Thickness ◽  
Plastic Relaxation

Investigation of Plastic Relaxation in Si1-xGex/Si Deposited by Selective Epitaxy

1998 ◽  
Vol 533 ◽  
Author(s):  
S. Wickenhäuser ◽  
L. Vescan
Keyword(s):  
Growth Temperature ◽  
Critical Thickness ◽  
Activation Barrier ◽  
Nucleation Site ◽  
Plastic Relaxation ◽  
Misfit Dislocations ◽  
Optical Micrograph ◽  
Site Density ◽  
Initial Stage ◽  
Nucleation Site Density

AbstractSi1-xGex/Si heterostructures with different layer thicknesses grown by selective LPCVD epitaxy at different growth temperatures were investigated with regard to plastic relaxation. AFM and optical micrograph were performed to determine the dislocation density. From the analysis of the misfit dislocations at the initial stage of relaxation of the samples grown at 700°C it was possible to determine the nucleation site density and an activation energy of 2.8 eV for the heterogeneous nucleation of misfit dislocations. While the critical thickness hc for a given Ge content increases with decreasing growth temperature between 800°C-680°C one observes a dramatic decay of hc, at a growth temperature of 625°C. For growth at 625°C it was found that this activation barrier is drastically decreased.

Critical Thickness for Onset of Plastic Relaxation in (11\bar22) and (20\bar21) Semipolar AlGaN Heterostructures

2010 ◽  
Vol 3 (11) ◽  
pp. 111002 ◽  
Author(s):  
Erin C. Young ◽  
Chad S. Gallinat ◽  
Alexey E. Romanov ◽  
Anurag Tyagi ◽  
Feng Wu ◽  
...  
Keyword(s):  
Critical Thickness ◽  
Plastic Relaxation

Si1−xGex Island Formation by Post-Growth Anneal on Supercritical Layers Grown by RPCVD

2000 ◽  
Vol 618 ◽  
Author(s):  
K. Grimm ◽  
L. Vescan ◽  
L.K. Nanver ◽  
C.C.G. Visser ◽  
H. Lüthl
Keyword(s):  
Epitaxial Growth ◽  
Low Temperatures ◽  
Critical Thickness ◽  
Plastic Relaxation ◽  
Size Distributions ◽  
Uniform Size ◽  
High Hydrogen ◽  
Strong Emission ◽  
Order Of Magnitude ◽  
Degree Of Control

ABSTRACTSiGe island layers have been created by post growth anneal on supercritical layers grown at low temperatures (500°C) and high hydrogen pressures (40 Torr). The epitaxial growth has been performed in a commercially available single wafer RPCVD reactor using SiH2Cl2 and GeH4 as precursor gasses. SiGe layers grown under these conditions exceed the critical thickness for the onset of elastic relaxation reported for lower hydrogen pressures as well as the critical thickness for plastic relaxation by more than one order of magnitude. A subsequent anneal step is used to form the islands. This procedure allows some degree of control in the formation of SiGe islands. High island densities and uniform size distributions were achieved. Photoluminescence as well as electroluminescence measurements of these layers show strong emission from SiGe.

Various technic for the measurement of step thickness on crystal surfaces

1978 ◽  
Vol 36 (1) ◽  
pp. 438-439
Author(s):  
C. Boulesteix ◽  
C. Colliex ◽  
C. Mory ◽  
B. Pardo ◽  
D. Renard
Keyword(s):  
Critical Thickness ◽  
Symmetric Case ◽  
Transmitted Intensity ◽  
Crystal Surfaces ◽  
Bright Field ◽  
Excited Wave ◽  
Highly Sensitive ◽  
Contrast Mechanisms ◽  
Step Thickness ◽  
Thickness Variations

Contrast mechanisms, which are responsible of the various types of image formation, are generally thickness dependant. In the following, two imaging modes in the 100 kV CTEM are described : they are highly sensitive to thickness variations and can be used for quantitative estimations of step heights.Detailed calculations (1) of the bright-field intensity have been carried out in the 3 (or 2N+l)-beam symmetric case. They show that in given conditions, the two important symmetric Bloch waves interfere most strongly at a critical thickness for which they have equal emergent amplitudes (the more excited wave at the entrance surface is also the more absorbed). The transmitted intensity I for a Nd2O3 specimen has been calculated as a function of thickness t. The capacity of the method to detect a step and measure its height can be more clearly deduced from a plot of dl/Idt as shown in fig. 1.

Structural properties of GaAs/InGaAs/GaAs (001) and InGaAs/GaAs (001) heterostructures and correlation with electronic properties

1990 ◽  
Vol 48 (4) ◽  
pp. 602-603
Author(s):  
J.M. Bonar ◽  
R. Hull ◽  
R. Malik ◽  
R. Ryan ◽  
J.F. Walker
Keyword(s):  
Band Gap ◽  
Electronic Properties ◽  
Gaas Substrate ◽  
Critical Thickness ◽  
Lattice Mismatch ◽  
Band Offset ◽  
Misfit Dislocations ◽  
Gaas Substrates ◽  
Gaas Structure ◽  
Low X

In this study we have examined a series of strained heteropeitaxial GaAs/InGaAs/GaAs and InGaAs/GaAs structures, both on (001) GaAs substrates. These heterostructures are potentially very interesting from a device standpoint because of improved band gap properties (InAs has a much smaller band gap than GaAs so there is a large band offset at the InGaAs/GaAs interface), and because of the much higher mobility of InAs. However, there is a 7.2% lattice mismatch between InAs and GaAs, so an InxGa1-xAs layer in a GaAs structure with even relatively low x will have a large amount of strain, and misfit dislocations are expected to form above some critical thickness. We attempt here to correlate the effect of misfit dislocations on the electronic properties of this material.The samples we examined consisted of 200Å InxGa1-xAs layered in a hetero-junction bipolar transistor (HBT) structure (InxGa1-xAs on top of a (001) GaAs buffer, followed by more GaAs, then a layer of AlGaAs and a GaAs cap), and a series consisting of a 200Å layer of InxGa1-xAs on a (001) GaAs substrate.

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.

Epitaxial Growth in Dislocation-Free Strained Alloy Films

2002 ◽  
Vol 715 ◽  
Author(s):  
Zhi-Feng Huang ◽  
Rashmi C. Desai
Keyword(s):  
Deposition Rate ◽  
Elastic Moduli ◽  
Composition Dependence ◽  
Critical Thickness ◽  
Lattice Misfit ◽  
Misfit Strain ◽  
Joint Stability ◽  
Alloy Films ◽  
The Stability ◽  
Stability Results

AbstractThe morphological and compositional instabilities in the heteroepitaxial strained alloy films have attracted intense interest from both experimentalists and theorists. To understand the mechanisms and properties for the generation of instabilities, we have developed a nonequilibrium, continuum model for the dislocation-free and coherent film systems. The early evolution processes of surface pro.les for both growing and postdeposition (non-growing) thin alloy films are studied through a linear stability analysis. We consider the coupling between top surface of the film and the underlying bulk, as well as the combination and interplay of different elastic effects. These e.ects are caused by filmsubstrate lattice misfit, composition dependence of film lattice constant (compositional stress), and composition dependence of both Young's and shear elastic moduli. The interplay of these factors as well as the growth temperature and deposition rate leads to rich and complicated stability results. For both the growing.lm and non-growing alloy free surface, we determine the stability conditions and diagrams for the system. These show the joint stability or instability for film morphology and compositional pro.les, as well as the asymmetry between tensile and compressive layers. The kinetic critical thickness for the onset of instability during.lm growth is also calculated, and its scaling behavior with respect to misfit strain and deposition rate determined. Our results have implications for real alloy growth systems such as SiGe and InGaAs, which agree with qualitative trends seen in recent experimental observations.

scholarly journals Transparent TiO2/Cu/TiO2 Multilayer for Electrothermal Application

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 1024
Author(s):  
Jingjing Peng ◽  
Changshan Hao ◽  
Hongyan Liu ◽  
Yue Yan
Keyword(s):  
Optical Properties ◽  
Heating Rate ◽  
Figure Of Merit ◽  
Annealing Temperature ◽  
Critical Thickness ◽  
Experimental Results ◽  
Tio2 Layer ◽  
Electrical And Optical Properties ◽  
Partial Crystallization

Highly transparent indium-free multilayers of TiO2/Cu/TiO2 were obtained by means of annealing. The effects of Cu thickness and annealing temperature on the electrical and optical properties were investigated. The critical thickness of Cu mid-layer with optimal electrical and optical properties was 10 nm, with the figure of merit reaching as high as 5 × 10−3 Ω−1. Partial crystallization of the TiO2 layer enhanced the electrical and optical properties upon annealing. Electrothermal experiments showed that temperatures of more than 100 °C can be reached at a heating rate of 2 °C/s without any damage to the multilayers. The experimental results indicate that reliable transparent TiO2/Cu/TiO2 multilayers can be used for electrothermal application.

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