Fabrication of a-Si:H/a-Al1−xOx Superlattice by Excimer Laser MOCVD and its Properties

1990 ◽  
Vol 201 ◽  
Author(s):  
K. Uwasawa ◽  
F. Ishihara ◽  
J. Wada ◽  
S. Matsumoto
Keyword(s):  
Size Effect ◽  
Layer Thickness ◽  
Excimer Laser ◽  
Optical Band Gap ◽  
Periodic Variation ◽  
Cross Sectional ◽  
Quantum Size ◽  
Sims Analysis ◽  
Arf Excimer Laser ◽  
Superlattice Structures

Abstracta-Si:H/a-A11−xOx superlattice structures have been fabricated by ArF excimer laser MOCVD. Periodic variation of composed elements in multilayers with quite uniform layer thickness was clearly shown by SIMS analysis. Optical band gap was increased with the decrease of the well layer thickness, indicating the quantum size effect. With the advantage of the inherent digital process, very sharp interface was obtained, which was confirmed by both XPS and cross sectional TEM analyses.

Quantum Size Effect of 2DEG Confined Within BaTiO3/SrTiO3:Nb Superlattices

2007 ◽  
Vol 1044 ◽  
Author(s):  
Yuki Nakanishi ◽  
Hiromichi Ohta ◽  
Teruyasu Mizoguchi ◽  
Yuichi Ikuhara ◽  
Kunihito Koumoto
Keyword(s):  
Size Effect ◽  
Seebeck Coefficient ◽  
Layer Thickness ◽  
Film Growth ◽  
Quantum Size Effect ◽  
Single Crystal Substrate ◽  
Cross Sectional ◽  
Insulating Layer ◽  
Quantum Size ◽  
Unit Cells

AbstractVery recently, we have found that the high density 2DEG (ne ∼1021 cm−3), which is confined within a unit cell layer thickness of SrTiO3, exhibits unusually large Seebeck coefficient (S2DEG/Sbulk ∼5)[1]. In the optimum, extremely high ZT2DEG of ∼2.4 can be obtained at room temperature, while the effective ZTeff. was only ∼0.24 because 9 unit cells of electrically insulating SrTiO3 layers were used to fabricate the 2DEG structure. Thus, high ZTeff can be realized if the insulating layer thickness is reduced significantly. We selected BaTiO3∼SrTiO3:Nb superlattice to reduce insulating layer thickness because dielectric constant of BaTiO3 is one order of magnitude large (∼3,000) as compared to that of SrTiO3 (∼300). We expected that the conduction electrons can be confined much strongly in the SrTiO3:Nb layer by sandwiching between highly dielectric BaTiO3 layers. As a result, we clarified that the critical BaTiO3 layer thickness is 1.2 nm, significantly small as compared to SrTiO3 layer (4 nm). The BaTiO3/SrTiO3:Nb superlattice films were fabricated by a pulsed laser deposition (PLD) method on (001)-face of LaAlO3 single crystal substrate at 900°C. During the film growth, we monitored RHEED intensity oscillation to control layer thickness precisely. Out-of-plane high-resolution X-ray diffraction measurements and cross sectional HAADF-STEM observations revealed that the resultant films were high quality BaTiO3/SrTiO3:Nb superlattice. Hall mobility of the SrTiO3:Nb layer was 0.4 cm2·V−1·s−1, while that of superlattice decreased gradually with increasing BaTiO3 layer thickness most likely due to that intra layer diffusion of Ba2+ ion occurred between BaTiO3 and SrTiO3:Nb layers[2], which was clearly observed by the EELS mapping. Seebeck coefficient |S|300K of SrTiO3:Nb layer was 57 μV·K−1, which corresponds carrier concentration ne of 5×1021 cm−3. The |S|300K value became large with decreasing the SrTiO3:Nb layer thickness (dSrTiO3:Nb) and it reached 305 μV·K−1, which is approximately 5 times larger than that of SrTiO3:Nb bulk. The slope of log |S|- log dSrTiO3:Nb plots was 1/2, suggesting that quantum size effect occurred. Critical BaTiO3 layer thickness for the quantum confinement of the electrons was 1.2 nm (3 unit cells of BaTiO3), which is significantly small as compared to SrTiO3 (4 nm). Thus, BaTiO3/SrTiO3:Nb superlattice would be a promising candidate to realize high ZTeff.

Reformulation of pairing theory

1988 ◽  
Vol 02 (05) ◽  
pp. 1101-1105 ◽  
Author(s):  
Miklos GULACSI ◽  
Zsolt GULACSI
Keyword(s):  
Transition Temperature ◽  
Size Effect ◽  
Layer Thickness ◽  
Short Communication ◽  
Cooper Pairing ◽  
Two Dimensional ◽  
Critical Transition ◽  
Critical Transition Temperature ◽  
Quantum Size ◽  
Natural Way

The original Cooper pairing theory is reformulated for electrons confined in a layer. This analysis is motivated by the quasi-two-dimensional character of the oxidic superconductors, in case of which the extension of the initial (3D) Cooper framework is practically impossible. By considering the electrons moving in a flat box, due to quantum size effect the properties of these oxidic superconductors can be explained in a natural way. In this short communication we will concentrate to the variation of the critical transition temperature due to the layer thickness and to the number of conduction (Cu-O) planes. The results are confirmed by the experiment. This being an evidence for the presence of the charge confinement effect in the oxidic superconductors.

Photoacoustic Measurement of a-Si:H/a-SiNx:H Superlattice Films

1986 ◽  
Vol 77 ◽  
Author(s):  
Feng Xiaomei ◽  
Liu Hsiangna ◽  
Wang Zhichao ◽  
Qiu Shuye ◽  
He Yuliang
Keyword(s):  
Absorption Coefficient ◽  
Size Effect ◽  
Layer Thickness ◽  
Optical Transmission ◽  
Transmission Spectra ◽  
Superlattice Structure ◽  
Quantum Size ◽  
Peak Intensity ◽  
Optical Transmission Spectra ◽  
Photoacoustic Measurement

ABSTRACTPhotoacoustic (PAS) and optical transmission spectra were measured on a-Si:H/a-SiNx:H superlattices. The absorption coefficient ∝ in the range 102∼104 cm-1 was obtained by converting the PAS signal to ∝. The enhancement of the PAS peak intensity Qs and the increase in the width of the Urbach edge with decreasing a-Si:H layer thickness are explained as results of quantum size effect in the superlattice structure.

Fluorescent carbon nano dots from lignite: unveiling the impeccable evidence for quantum confinement

2016 ◽  
Vol 18 (17) ◽  
pp. 12065-12073 ◽  
Author(s):  
Senthil Kumar Thiyagarajan ◽  
Suresh Raghupathy ◽  
Dharmalingam Palanivel ◽  
Kaviyarasan Raji ◽  
Perumal Ramamurthy
Keyword(s):  
Laser Ablation ◽  
Size Effect ◽  
Band Gap ◽  
Quantum Confinement ◽  
Optical Band Gap ◽  
Pulsed Laser ◽  
Pulsed Laser Ablation ◽  
Quantum Size Effect ◽  
Quantum Size ◽  
Fluorescent Carbon

Pulsed laser ablation of lignite in EDA solution exfoliates CDs (CD3) which exhibit the influence of quantum size effect in tuning the optical band gap of CDs.

The stabilization of B.C.C. Cu in Cu/Nb nanolayered composites

1996 ◽  
Vol 54 ◽  
pp. 228-229
Author(s):  
H. Kung ◽  
A.J. Griffin ◽  
Y.C. Lu ◽  
K.E. Sickafus ◽  
T.E. Mitchell ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Layer Thickness ◽  
Volume Fraction ◽  
Ion Beam ◽  
High Strength ◽  
Cross Sectional ◽  
Metastable Structure ◽  
High Resolution Tem ◽  
Potential Improvement ◽  
Two Phases

Materials with compositionally modulated structures have gained much attention recently due to potential improvement in electrical, magnetic and mechanical properties. Specifically, Cu-Nb laminate systems have been extensively studied mainly due to the combination of high strength, and superior thermal and electrical conductivity that can be obtained and optimized for the different applications. The effect of layer thickness on the hardness, residual stress and electrical resistivity has been investigated. In general, increases in hardness and electrical resistivity have been observed with decreasing layer thickness. In addition, reduction in structural scale has caused the formation of a metastable structure which exhibits uniquely different properties. In this study, we report the formation of b.c.c. Cu in highly textured Cu/Nb nanolayers. A series of Cu/Nb nanolayered films, with alternating Cu and Nb layers, were prepared by dc magnetron sputtering onto Si {100} wafers. The nominal total thickness of each layered film was 1 μm. The layer thickness was varied between 1 nm and 500 nm with the volume fraction of the two phases kept constant at 50%. The deposition rates and film densities were determined through a combination of profilometry and ion beam analysis techniques. Cross-sectional transmission electron microscopy (XTEM) was used to examine the structure, phase and grain size distribution of the as-sputtered films. A JEOL 3000F high resolution TEM was used to characterize the microstructure.

High Resolution Displacement of Functional Groups onto Fluorocarbon Resin Surface by Using ArF Excimer Laser

1996 ◽  
Vol 451 ◽  
Author(s):  
T. Shimizu ◽  
M. Murahara
Keyword(s):  
Contact Angle ◽  
High Resolution ◽  
Laser Beam ◽  
Thin Layer ◽  
Functional Groups ◽  
Excimer Laser ◽  
Laser Fluence ◽  
Large Area ◽  
Three Solutions ◽  
Arf Excimer Laser

ABSTRACTA Fluorocarbon resin surface was selectively modified by irradiation with a ArF laser beam through a thin layer of NaAlO2, B(OH)3, or H2O solution to give a hydrophilic property. As a result, with low fluence, the surface was most effectively modified with the NaAlO2 solution among the three solutions. However, the contact angle in this case changed by 10 degrees as the fluence changed only 1mJ/cm2. When modifying a large area of the surface, high resolution displacement could not be achieved because the laser beam was not uniform in displacing functional groups. Thus, the laser fluence was successfully made uniform by homogenizing the laser beam; the functional groups were replaced on the fluorocarbon resin surface with high resolution, which was successfully modified to be hydrophilic by distributing the laser fluence uniformly.

scholarly journals Integrated backscatter-intravascular ultrasound and modification of plaque during excimer laser coronary angioplasty

2021 ◽  
Author(s):  
Satoru Sasaki ◽  
Kenji Nakajima ◽  
Keizo Watanabe ◽  
Yudai Nozaki ◽  
Tadashi Yuguchi ◽  
...  
Keyword(s):  
Intravascular Ultrasound ◽  
Excimer Laser ◽  
Coronary Angioplasty ◽  
Coronary Plaque ◽  
Cross Sectional ◽  
Integrated Backscatter ◽  
Before And After ◽  
Vessel Volume ◽  
Integrated Backscatter Intravascular Ultrasound ◽  
Excimer Laser Coronary Angioplasty

AbstractThis study aims to test the hypothesis that the effect of excimer laser coronary angioplasty (ELCA) not only vaporizes thrombi and their underlying coronary plaque, it also changes their quality. We performed a series of cross-sectional analyses in 52 lesions in 51 patients before and after ELCA with integrated backscatter-intravascular ultrasound (IB-IVUS). The constituent parts of the plaque can be assessed by IB-IVUS (i.e., calcified, fibrous, lipid) according to integrated backscatter values. Minimum lumen diameter, lumen volume and vessel volume expanded after ELCA, while plaque volume did not significantly decrease. There was also a decrease of ‘lipid’ component (35.4–30.3%, P < 0.001) and an increase of IB-IVUS-derived ‘fibrous’ part (34.5–38.3%, P < 0.001). These results may help in understanding plaque change after ELCA. Excimer laser coronary angioplasty seems to contribute to the modification of coronary plaque composition in addition to debulking it.

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