Interdiffusion Mechanisms in GaAs/AlGaAs Quantum Well Heterostructures Induced by SiO2 Capping and Annealing

1997 ◽  
Vol 484 ◽  
Author(s):  
A. Pépin ◽  
C. Vieu ◽  
M. Schneider ◽  
H. Launois ◽  
E. V. K. Rao
Keyword(s):  
Quantum Well ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Semiconductor Surface ◽  
Simultaneous Generation ◽  
Spatial Control ◽  
Thermal Chemical Vapor Deposition ◽  
Thermal Expansion Coefficients ◽  
Expansion Coefficients ◽  
The Difference

AbstractWe have investigated intermixing enhancement in GaAs/AlGaAs quantum well heterostructures achieved by SiO2 capping obtained by rapid thermal chemical vapor deposition. Evidence of fast Ga pumping inside the SiO2 layer during anneal and simultaneous generation of excess Ga vacancies under the SiO2/GaAs interface is presented. A simple model involving the thermal stress arising from the difference in thermal expansion coefficients between SiO2 and GaAs, is proposed to account for the abnormally fast Ga vacancy diffusion inside the heterostructure. A spatial control of the interdiffused areas can be achieved if a suitable stress field is imposed on the semiconductor surface by the capping layers. We show experimental evidence of this effect using a specific patterning of SiO2/Si3N4 bilayers.

Defects in β-SiC thin films grown on α-SiC substrates

1988 ◽  
Vol 46 ◽  
pp. 568-569
Author(s):  
Karren L. More
Keyword(s):  
Thin Films ◽  
Semiconductor Device ◽  
Lattice Mismatch ◽  
Chemical Vapor ◽  
Substrate Material ◽  
Growth Interface ◽  
Si Substrates ◽  
Thermal Expansion Coefficients ◽  
Device Applications ◽  
Expansion Coefficients

Beta-SiC is an ideal candidate material for use in semiconductor device applications. Currently, monocrystalline β-SiC thin films are epitaxially grown on {100} Si substrates by chemical vapor deposition (CVD). These films, however, contain a high density of defects such as stacking faults, microtwins, and antiphase boundaries (APBs) as a result of the 20% lattice mismatch across the growth interface and an 8% difference in thermal expansion coefficients between Si and SiC. An ideal substrate material for the growth of β-SiC is α-SiC. Unfortunately, high purity, bulk α-SiC single crystals are very difficult to grow. The major source of SiC suitable for use as a substrate material is the random growth of {0001} 6H α-SiC crystals in an Acheson furnace used to make SiC grit for abrasive applications. To prepare clean, atomically smooth surfaces, the substrates are oxidized at 1473 K in flowing 02 for 1.5 h which removes ∽50 nm of the as-grown surface. The natural {0001} surface can terminate as either a Si (0001) layer or as a C (0001) layer.

Influence of Magnetoelastic Anisotropy on Properties of Nanostructured Microwires

2013 ◽  
Vol 646 ◽  
pp. 59-66 ◽  
Author(s):  
Arcady Zhukov ◽  
Margarita Churyukanova ◽  
Lorena Gonzalez-Legarreta ◽  
Ahmed Talaat ◽  
Valentina Zhukova ◽  
...  
Keyword(s):  
Heat Capacity ◽  
Hysteresis Loops ◽  
Magnetic Behaviour ◽  
Soft Magnetic ◽  
Magnetoelastic Anisotropy ◽  
Thermal Expansion Coefficients ◽  
Magnetoelastic Energy ◽  
Expansion Coefficients ◽  
The Difference ◽  
Magneto Resistance

We studied the effect ofthe magnetoelastic ansitropy on properties of nanostructured glass-coated microwires with soft magnetic behaviour (Finemet-type microwires of Fe70.8Cu1Nb3.1Si14.5B10.6, Fe71.8Cu1Nb3.1Si15B9.1 and Fe73.8Cu1Nb3.1Si13B9.1 compositions) and with granular structure (Cu based Co-Cu microwires). The magnetoelastic energy originated from the difference in thermal expansion coefficients of the glass and metallic alloy during the microwires fabrication, affected the hysteresis loops, coercivity and heat capacity of Finemet-type microwires. Hysteresis loops of all as-prepared microwires showed rectangular shape, typical for Fe-rich microwires. As expected, coercivity, HC, of as-prepared microwires increases with decreasing of the ratio ρ defined as the ratio between the metallic nucleus diameter, d to total microwire diameter, D. On the other hand we observed change of heat capacity in microwires with different ratio ρ. In the case of Co-Cu microwires ρ- ratio affected the structure and the giant magneto-resistance of obtained microwires.

Growth of Single Crystalline ZnO Nanotubes and Nanosquids

2007 ◽  
Vol 1057 ◽  
Author(s):  
Abhishek Prasad ◽  
Samuel Mensah ◽  
Jiesheng Wang ◽  
Archana Pandey ◽  
Yoke Khin Yap
Keyword(s):  
Vapor Deposition ◽  
Self Assembly ◽  
Chemical Vapor ◽  
Zno Nanostructures ◽  
X Ray ◽  
Thermal Chemical Vapor Deposition ◽  
Crystal Growth Mechanism ◽  
Zno Nanotubes ◽  
Solid Crystal

ABSTRACTThe growth of ZnO nanotubes and nanosquids is obtained by conventional thermal chemical vapor deposition (CVD) without the use of catalysts or templates. Characterization of these ZnO nanostructures was conducted by X-ray powder diffraction (XRD), Field-emission scanning electron microscopy (FESEM), Raman spectroscopy, and photoluminescence (PL). Results indicate that these ZnO nanostructures maintain the crystalline structures of the bulk wurtzite ZnO crystals. Our results show that rapid cooling can be used to induce the formation of ZnO nanotubes and ZnO nanosquids. The self-assembly of these novel ZnO nanostructures are guided by the theory of nucleation and the vapor-solid crystal growth mechanism.

Sign in / Sign up

Export Citation Format

Share Document