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Hot electron attenuation of direct and scattered carriers across an epitaxial Schottky interface  [PDF]
S. Parui,P. S. Klandermans,S. Venkatesan,C. Scheu,T. Banerjee
Physics , 2013, DOI: 10.1088/0953-8984/25/44/445005
Abstract: Hot electron transport of direct and scattered carriers across an epitaxial NiSi_2/n-Si(111) interface, for different NiSi_2 thickness, is studied using Ballistic Electron Emission Microscopy (BEEM). We find the BEEM transmission for the scattered hot electrons in NiSi_2 to be significantly lower than that for the direct hot electrons, for all thicknesses. Interestingly, the attenuation length of the scattered hot electrons is found to be twice larger than that of the direct hot electrons. The lower BEEM transmission for the scattered hot electrons is due to inelastic scattering of the injected hot holes while the larger attenuation length of the scattered hot electrons is a consequence of the differences in the energy distribution of the injected and scattered hot electrons and the increasing attenuation length, at lower energies, of the direct hot electrons in NiSi_2.
Comparison of hot-electron transmission in ferromagnetic Ni on epitaxial and polycrystalline Schottky interfaces  [PDF]
S. Parui,K. G. Rana,L. Bignardi,P. Rudolf,B. J. van Wees,T. Banerjee
Physics , 2013, DOI: 10.1103/PhysRevB.85.235416
Abstract: The hot-electron attenuation length in Ni is measured as a function of energy across two different Schottky interfaces viz. a polycrystalline Si(111)/Au and an epitaxial Si(111)/NiSi_2 interface using ballistic electron emission microscopy (BEEM). For similarly prepared Si(111) substrates and identical Ni thickness, the BEEM transmission is found to be lower for the polycrystalline interface than for the epitaxial interface. However, in both cases, the hot-electron attenuation length in Ni is found to be the same. This is elucidated by the temperature-independent inelastic scattering, transmission probabilities across the Schottky interface, and scattering at dissimilar interfaces.
Measurements of Spin Polarization of Epitaxial SrRuO3 Thin Films  [PDF]
B. Nadgorny,M. S. Osofsky,D. J. Singh,G. T. Woods,R. J. Soulen, Jr.,M. K. Lee,S. D. Bu,C. B. Eom
Physics , 2002, DOI: 10.1063/1.1539551
Abstract: We have measured the transport spin-polarization of epitaxial thin films of the conductive ferromagnetic oxide, SrRuO3, using Point Contact Andreev Reflection Spectroscopy (PCAR). In spite of the fact that spin-up and spin-down electronic densities of states at the Fermi level for SrRuO3 calculated from band structure theory are practically the same, the experimental transport spin polarization for these films was found to be about 50%. This result is a direct consequence of the Fermi velocity disparity between the majority and minority bands and is in good agreement with our theoretical estimates.
SiC epitaxial layers grown by chemical vapour deposition and the fabrication of Schottky barrier diodes

Wang Yue-Hu,Zhang Yi-Men,Zhang Yu-Ming,Zhang Lin,Jia Ren-Xu,Chen Da,

中国物理 B , 2010,
Abstract: This paper presents the results of unintentionally doped 4H-SiC epilayers grown on n-type Si-faced 4H-SiC substrates with 8° off-axis toward the 11\overline 2 0] direction by low pressure horizontal hot-wall chemical vapour deposition. Growth temperature and pressure are 1580~°C and 104~Pa, respectively. Good surface morphology of the sample is observed using atomic force microscopy (AFM) and scanning electron microscopy (SEM). Fourier transform infrared spectroscopy (FTIR) and x-ray diffraction (XRD) are used to characterize epitaxial layer thickness and the structural quality of the films respectively. The carrier concentration in the unintentional 4H-SiC homoepitaxial layer is about 6.4×1014~cm-3 obtained by c--V measurements. Schottky barrier diodes (SBDs) are fabricated on the epitaxial wafer in order to verify the quality of the wafer and to obtain information about the correlation between background impurity and electrical properties of the devices. Ni and Ti/4H-SiC Schottky barrier diodes with very good performances were obtained and their ideality factors are 1.10 and 1.05 respectively.
Characterization of the Schottky Barrier in SrRuO3/Nb:SrTiO3 Junctions  [PDF]
Y. Hikita,Y. Kozuka,T. Susaki,H. Takagi,H. Y. Hwang
Physics , 2007, DOI: 10.1063/1.2719157
Abstract: Internal photoemission spectroscopy was used to determine the Schottky barrier height in rectifying SrRuO3/Nb-doped SrTiO3 junctions for 0.01 wt % and 0.5 wt % Nb concentrations. Good agreement was obtained with the barrier height deduced from capacitance-voltage measurements, provided that a model of the nonlinear permittivity of SrTiO3 was incorporated in extrapolating the built-in potential, particularly for high Nb concentrations. Given the generic polarizability of perovskites under internal/external electric fields, internal photoemission provides a valuable independent probe of the interface electronic structure.
Observation of Spin-glass-like Behavior in SrRuO3 Epitaxial Thin Films  [PDF]
R Palai,H Huhtinen,R. S. Katiyar,J. F. Scott
Physics , 2007, DOI: 10.1103/PhysRevB.79.104413
Abstract: We report the observation of spin-glass-like behavior and strong magnetic anisotropy in extremely smooth (~1-3 \AA) roughness) epitaxial (110) and (010) SrRuO3 thin films. The easy axis of magnetization is always perpendicular to the plane of the film (unidirectional) irrespective of crystallographic orientation. An attempt has been made to understand the nature and origin of spin-glass behavior, which fits well with Heisenberg model.
Effects of Cr substitution on the magnetic and transport properties and electronic states of SrRuO3 epitaxial thin films  [PDF]
Kaori Kurita,Akira Chikamatsu,Kei Shigematsu,Tsukasa Katayama,Hiroshi Kumigashira,Tomoteru Fukumura,Tetsuya Hasegawa
Physics , 2015, DOI: 10.1103/PhysRevB.92.115153
Abstract: The effect of Cr substitution in a SrRuO3 epitaxial thin film on SrTiO3 substrate was investigated by measuring the magnetic and transport properties and the electronic states. The ferromagnetic transition temperature of the SrRu0.9Cr0.1O3 film (166 K) was higher than that of the SrRuO3 film (147 K). Resonant photoemission spectroscopy experimentally revealed that the Cr 3dt2g orbital is hybridized with the Ru 4dt2g orbital in the SrRu0.9Cr0.1O3 film, supporting the assumption that the enhancement of the ferromagnetic transition temperature through Cr substitution stems from the widening of energy bands due to the hybridization of Cr 3dt2g and Ru 4dt2g orbitals. Furthermore, we found that the Hall resistivity of the SrRu0.9Cr0.1O3 film at low temperature is not a linear function of magnetic field in the high-field region where the out-of-plane magnetization was saturated; this result suggests that the SrRu0.9Cr0.1O3 film undergoes a structural transition at low temperature accompanied with the modulation of the Fermi surface.
Epitaxial strain induced magnetic transitions and phonon instabilities of the tetragonal SrRuO3  [PDF]
He He,Hang-Chen Ding,Yong-Chao Gao,Shi-Jing Gong,Xiangang Wan,Chun-Gang Duan
Physics , 2012, DOI: 10.1088/0953-8984/25/16/165504
Abstract: Using density-functional theory calculations, we investigate the magnetic as well as the dynamical properties of tetragonal SrRuO3 (SRO) under the influence of epitaxial strain. It is found that both the tensile and compressive strain in the xy-plane could induce the abrupt change in the magnetic moment of Ru atom. In particular, under the in-plane ~4% compressive strain, a ferromagnetic to nonmagnetic transition is induced. Whereas for the tensile strain larger than 3%, the Ru magnetic moment drops gradually with the increase of the strain, exhibiting a weak ferromagnetic state. We find that such magnetic transitions could be qualitatively explained by the Stoner model. In addition, frozen phonon calculations at {\Gamma} point reveal structural instabilities could occur under both compressive and tensile strains. Such instabilities are very similar to those of the ferroelectric perovskite oxides, even though SRO remains to be metallic in the range we studied. These might have influence on the physical properties of oxide supercells taking SRO as constituent.
Strain-induced single-domain growth of epitaxial SrRuO3 layers on SrTiO3: a high-temperature x-ray diffraction study  [PDF]
Arturas Vailionis,Wolter Siemons,Gertjan Koster
Physics , 2007, DOI: 10.1063/1.2771087
Abstract: Temperature dependent structural phase transitions of SrRuO3 thin films epitaxially grown on SrTiO3(001) single crystal substrates have been studied using high-resolution x-ray diffraction. In contrast to bulk SrRuO3, coherently strained epitaxial layers do not display cubic symmetry up to ~730 oC and remain tetragonal. Such behavior is believed to be induced by compressive strain between the SrRuO3 layer and SrTiO3 substrate due to lattice mismatch. The tetragonal symmetry during growth explains the single domain growth on miscut SrTiO3 substrates with step edges running along the [100] or [010] direction.
Schottky barrier and attenuation length for hot hole injection in non-epitaxial Au on p-type GaAs  [PDF]
I. Sitnitsky,J. J. Garramone,J. R. Abel,P. Xu,S. D. Barber,M. L. Ackerman,J. K. Schoelz,P. M. Thibado,V. P. LaBella
Physics , 2015,
Abstract: Ballistic electron emission microscopy (BEEM) was performed to obtain nanoscale current versus bias characteristics of non-epitaxial Au on p-type GaAs in order to accurately measure the local Schottky barrier height. Hole injection BEEM data was averaged from thousands of spectra for various metal film thicknesses and then used to determine the attenuation length of the energetic charge carriers as a function of tip bias. We report the marked increase in attenuation length at biases near the Schottky barrier, providing evidence for the existence of coherent BEEM currents in Schottky diodes. These results provide additional evidence against the randomization of a charge carrier's momentum at the metal-semiconductor interface.
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