Raman Scattering Characterization of GaAs-AlAs Superlattices Grown Along the [110] Direction

1987 ◽  
Vol 102 ◽  
Author(s):  
D. Kirillov ◽  
Yi-Ching Pao
Keyword(s):  
Raman Scattering ◽  
Molecular Beam ◽  
Transverse Optical ◽  
Crystallographic Structure ◽  
Optical Phonons ◽  
Lower Intensity ◽  
Dominant Feature ◽  
First Time

ABSTRACTRaman spectra of the GaAs-AlAs superlattice grown by molecular beam epi-taxy along the [110] direction were studied for the first time. The spectra were compared with spectra of the [100] superlattice and differences due to different crystallographic structure were analyzed. It was found that the energies of folded acoustical modes are higher in the [110] superlattice due to higher sound velocity in the [110] direction. Confined transverse optical phonons were a dominant feature of the spectrum of the [110] superlattice which allowed observation of the folding of transverse optical phonons. Stronger intensity of interface modes and lower intensity of folded acousti-cal modes in the [110] superlattice indicated that the quality of the layer interfaces was worse than in the [100] superlattice.

Photoluminescence Characterization of SiGe/Si Quantum-Well Wire Structures

1995 ◽  
Vol 379 ◽  
Author(s):  
S. Nilsson ◽  
H. P. Zeindl ◽  
A. Wolff ◽  
K. Pressel
Keyword(s):  
Quantum Well ◽  
Room Temperature ◽  
Molecular Beam ◽  
Optical Quality ◽  
Photoluminescence Spectra ◽  
Single Quantum Well ◽  
Quantum Well Wire ◽  
Carbon Interstitial

ABSTRACTLow-temperature photoluminescence measurements were performed in order to probe the optical quality of SiGe/Si quantum-well wire structures fabricated by electron-beam lithography and subsequent reactive ion etching, having the patterned polymethylmethacrylate resist as an etch mask. In addition, one set of quantum-well wire structures was post-treated by means of annealing in a hydrogen environment. Our results show that even for the smallest wires of about 100nm in width, the wires exhibit phonon-resolved photoluminescence spectra, similar to that from the molecular beam eptitaxially grown SiGe single quantum well which was used as starting material for the patterning process. After the patterning process a new sharp peak appears in the photoluminescence spectra at 0.97eV in photon energy. Our investigation suggests that this feature is introduced by damage during the patterning process and most probably identical to the G-line, which previously was identified as originating from the dicarbon centre (substitutional carbon-interstitial carbon) in Si. This centre is known to be a very common endproduct of irradiating Si near room temperature which is the case at our patterning process.

Step Profile Fluctuations in Quantum-Well Wire Growth on Vicinal Surfaces

1989 ◽  
Vol 160 ◽  
Author(s):  
K.J. Hugill ◽  
T. Shitara ◽  
S. Clarke ◽  
D.D. Vvedensky ◽  
B.A. Joyce
Keyword(s):  
Quantum Well ◽  
Molecular Beam ◽  
Solid Model ◽  
Optimum Regime ◽  
Vicinal Surfaces ◽  
Quantum Well Wire ◽  
Quantum Well Wires ◽  
Edge Stability

AbstractMolecular-beam epitaxy of quantum-well wires on vicinal surfaces is studied by application of Monte Carlo simulations of a solid-on-solid model. Characterization of simulated quantum-well wires indicates an optimum regime within which the quality of the quantum-well wire is maximized. The model is extended to include observed anisotropies in GaAs growth on vicinal surfaces, and the conclusion is reached that better quality quantum-well wires may be grown on substrates misoriented from the (001) towards [110], rather than [110], due to relative step edge stability on the two misoriented surfaces.

MBE Growth and Characterization of CdTe, ZnTe Epilayers and CdTe/ZnCdTe Superlattices on GaAs Substrates

1992 ◽  
Vol 263 ◽  
Author(s):  
A.E. Milokhin ◽  
I.E. Trofimov ◽  
M.V. Petrov ◽  
F.F. Balakirev ◽  
V.D. Kuzmin ◽  
...  
Keyword(s):  
Raman Scattering ◽  
Buffer Layer ◽  
Lattice Constant ◽  
Strong Influence ◽  
High Crystalline Quality ◽  
Mbe Growth ◽  
X Ray ◽  
Gaas Substrates

Semiconductor heterostuctures ZnxCd1−xTe/CdTe were found to be of interest recently due to their potential practical usage. The reason for this is the beautiful variety of electrical heterostucture properties which arise from the strong influence of elastic deformation distribution. Thin epilayer films and superlattices ZnxCd1−xTe/CdTe were prepared on GaAs semi-isolator substrates by MBE technology with RHEED oscillation measurements of the deposited layers. X-ray measurements have shown high crystalline quality of the samples.We have performed Raman scattering studies of ZnxZnxCd1−xTe/CdTe structures. The data obtained were interpreted as a proff of the pseudomorphous growth model. That is, ZnxCd1−xTe/CdTe SLS keeps the lattice constant of the buffer layer.

scholarly journals Ampelographic and oenological characterization of the ancient grapevine cv. Dobričić grown in the coastal region of Croatia

OENO One ◽  
2012 ◽  
Vol 46 (4) ◽  
pp. 263
Author(s):  
Goran Zdunić ◽  
Irena Budić-Leto ◽  
Urska Vrhovsek ◽  
Iva Tomić-Potrebuješ ◽  
Edi Maletić
Keyword(s):  
Coastal Region ◽  
Red Wines ◽  
High Quality ◽  
Virus Incidence ◽  
High Virus ◽  
First Time ◽  
Outstanding Quality ◽  
Selection Of

<p style="text-align: justify;"><strong>Aims</strong>:A four-year study (2007 through 2010) was carried out to determine agronomic, biological, and oenological characteristics of Dobričić grapevines so as to evaluate this cultivar and protect it from extinction.</p><p style="text-align: justify;"><strong>Methods and results</strong>: 38 characteristics from the OIV descriptor list were used to describe young shoot, mature leaf, cluster, and berry morphology of Dobričić grapevines. The dimensions of an average leaf were constructed from measured leaf variables. A typical Dobričić genotype at nine microsatellite loci is presented. ELISA analysis revealed high virus incidence and all samples tested were GLRaV-3 positive. The profile of different classes of polyphenols in Dobričić wine was determined using HPLC and spectrophotometry. The concentrations of polyphenols in Dobričić wine, especially anthocyanins, hydroxycinnamic acids and stilbenes, were high compared to major red wines reported in the literature. Descriptive sensory analysis was carried out to determine the aroma attributes describing a Dobričić monovarietal wine.</p><p style="text-align: justify;"><strong>Conclusion</strong>: Knowledge of the biodiversity of the grapevine cultivars of Croatia is still scant. This study provides for the first time ampelographic and oenological information on Dobričić grapevines and demonstrates its high quality potential.</p><p style="text-align: justify;"><strong>Significance and impact of the study</strong>: The results of the ampelographic characterization would be helpful in the identification and selection of Dobričić for cultivation in certain vine-growing areas. The outstanding quality of Dobričić makes it very promising for wine blending (colour improvement) and plant breeding purposes.</p>

Molecular beam homoepitaxial growth of MgO(001)

1994 ◽  
Vol 9 (11) ◽  
pp. 2944-2952 ◽  
Author(s):  
S.A. Chambers ◽  
T.T. Tran ◽  
T.A. Hileman
Keyword(s):  
Electron Spectroscopy ◽  
High Speed ◽  
Molecular Beam ◽  
Step Flow ◽  
Homoepitaxial Growth ◽  
Crystallographic Order ◽  
Step Flow Growth ◽  
First Time

We describe homoepitaxial growth and detailed in situ characterization of MgO(001). We have used, for the first time, high-speed Auger electron spectroscopy as a real-time probe of film composition during growth. Excellent short-range and long-range crystallographic order are achieved in films grown to a thickness of several hundred angstroms in the substrate temperature range of 450 °C to 750 °C. Moreover, the films become more laminar as the growth temperature increases, suggesting that MgO grows homoepitaxially by the step-flow growth mechanism at elevated temperature. The surfaces of films grown at 650°and 750 °C are smoother than those obtained by cleaving MgO(001).

Fabrication and characterization of ZnMgO nanowalls grown on 4H-SiC by molecular beam epitaxy

2019 ◽  
Vol 52 (1) ◽  
pp. 168-170
Author(s):  
Mieczyslaw A. Pietrzyk ◽  
Aleksandra Wierzbicka ◽  
Marcin Stachowicz ◽  
Dawid Jarosz ◽  
Adrian Kozanecki
Keyword(s):  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
Optoelectronic Devices ◽  
Growth Conditions ◽  
Buffer Layers ◽  
X Ray Diffraction ◽  
X Ray ◽  
Fabrication And Characterization

Control of nanostructure growth is a prerequisite for the development of electronic and optoelectronic devices. This paper reports the growth conditions and structural properties of ZnMgO nanowalls grown on the Si face of 4H-SiC substrates by molecular beam epitaxy without catalysts and buffer layers. Images from scanning electron microscopy revealed that the ZnMgO nanowalls are arranged in parallel rows following the stripe morphology of the SiC surface, and their thickness is around 15 nm. The crystal quality of the structures was evaluated by X-ray diffraction measurements.

scholarly journals Rapid Rubber Extraction and NMR Spectroscopy of Rubber, Extracted from the Endemic Species Scorzonera Tau-Saghyz

2020 ◽  
Vol 22 (1) ◽  
pp. 59
Author(s):  
K.K. Boguspaev ◽  
S.K. Turasheva ◽  
T.M. Seilkhanov ◽  
D.G. Faleev ◽  
M.S. Mutalkhanov ◽  
...  
Keyword(s):  
Adventitious Shoots ◽  
Physiological Age ◽  
Root Extract ◽  
Nmr Characterization ◽  
First Time ◽  
Rubber Good ◽  
Isoprene Rubber

Scorzonera tau-saghyz Lipsch. et G.G. Bosse is an endemic rubber producing plant, growing in mountain regions in South Kazakhstan. The rubber content in plants and the quality of biopolymer has an important impact on industrial rubber production. The results of this study showed that the amount of rubber in S. tau-saghyz roots fluctuates between 7.74% and 38.75%. The amount of synthesized and deposited rubber biopolymer particles depends on various factors such as physiological age of plant, origin, temperature, moisture and environmental conditions. We optimized the extraction method of natural rubber by using n-hexane as a solvent for direct extraction. This method allows extracting the maximum amount of rubber from 3‒4-year-old plants. NMR results show structural links of natural isoprene rubber in the root extract sample. There is a clear relationship between methyl, methine and methylene protons which corresponds to isoprene rubber structure. The samples having strongly marked singlets that are inherent for rubber functional groups confirms the stereospecific structure of rubber. Good solubility of the root extract in deuterated chloroform can characterize the low molecular weight of the polymer. NMR characterization of rubber, extracted from S. tau-saghyz roots, is reported for the first time. Regeneration in vitro provides an important opportunity for endemic preservation by rapidly increasing the number of plants. The best regeneration of adventitious shoots was obtained on MS medium containing 5.5 μM kinetin and 0.5 μM NAA. The plants were successfully acclimatized in a glasshouse with 75% of S. tau-saghyz plantlets, respectively surviving after transfer to ex vitro conditions.

Sign in / Sign up

Export Citation Format

Share Document