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Abstract: Ten layers of self-assembled InMnAs quantum dots with InGaAs barrier were grown on high resistivity (100) p-type GaAs substrates by molecular beam epitaxy (MBE). The presence of ferromagnetic structure was confirmed in the InMnAs diluted magnetic quantum dots. The ten layers of self-assembled InMnAs quantum dots were found to be semiconducting, and have ferromagnetic ordering with a Curie temperature, T C=80K. It is likely that the ferromagnetic exchange coupling of sample with T C=80K is hole mediated resulting in Mn substituting In and is due to the bound magnetic polarons co-existing in the system. PL emission spectra of InMnAs samples grown at temperature of 275, 260 and 240°C show that the interband transition peak centered at 1.31eV coming from the InMnAs quantum dot blueshifts because of the strong confinement effects with increasing growth temperature. [ABSTRACT FROM AUTHOR]

Abstract: The excitation density dependent photoluminescence (PL) spectra in Ga1−x Mn x N layers (where x≈0.1–0.8%) grown on sapphire (0001) substrates using the plasma-enhanced molecular beam epitaxy technique have been investigated. The efficient PL peaks are observed in the red (1.86eV), yellow (2.34eV), and blue (3.29eV) spectral ranges. By examining the dependence of PL on the excitation laser power density at 15 and 300K, the yellow band (2.34eV) and bandgap (3.50eV) luminescence vary linearly with the light intensity, which are in good agreement with a simple recombination model, which assumes a density of recombination centers below the conduction band edge. [ABSTRACT FROM AUTHOR]

Abstract We calculate the formation enthalpies of PdH x (x = 0 – 3) by cluster expansion (CE) and calculations based on density functional theory. CE predicts the stable palladium hydride structures PdH, PdH 2.67 , and PdH 2.75. The band structures and density of states indicate that the amount of hydrogen in the palladium lattice does not alter the metallic character of the palladium significantly. However, all PdH x structures with x > 1 have greater formation enthalpies than that of the given reaction path 4 PdH 2 = 2 PdH + 2 Pd + 3 H 2 and thus they are thermodynamically unstable. The shorter bond length of Pd–H and the smaller bond angle of Pd–H–Pd imply a higher cohesive energy in zincblende (ZB) PdH than that in rocksalt (RS) PdH. Bader charge analysis shows a stronger electronegativity of H atoms in ZB-PdH than that in RS-PdH. This results in a stronger Pd–H bond in ZB-PdH than that in RS-PdH. Thus ZB-PdH has lower formation enthalpy than that of RS-PdH. However, regarding the dynamic stability, we conclude that hydrogen atoms prefer to occupy the octahedral sites of the palladium lattice because of the lower zero-point energy and vibration free energy than that of occupying the tetrahedral sites. Graphical abstract Image 1 Highlights • Three intermediate ground-state structures PdH, PdH 2.67 , and PdH 2.75 are predicted. • The metallic character of Pd is almost impervious to the H content. • Zincblende PdH is more thermodynamically stable than rocksalt structure. • Regarding the dynamic stability, H atoms prefer to occupy the octahedral sites. [ABSTRACT FROM AUTHOR]

Monolayer (ML)-molybdenum disulfide (MoS 2 ) with a direct band gap of ~1.8 eV exhibits considerable potential for advanced electronic and optical device applications. The surface electronic properties of ML-MoS 2 need to be controlled for developing novel MoS 2 -based devices. In this study, we investigated the work function variation of chemical vapor deposition-grown ML-MoS 2 that was controlled by proton irradiation. The crystallinity of the ML-MoS 2 was confirmed by micro-Raman and Photoluminescence measurements. The work functions of the ML-MoS 2 irradiated with varying proton beam flux were measured by Kelvin probe force microscopy. As the ML-MoS 2 were exposed to the proton beam flux ranging from 1 × 10 12 to 1 × 10 14 protons/cm 2 at the same beam energy of 10 MeV, the contact potential difference of the MoS 2 increased up to about 0.108 V with increased proton beam flux. Based on the referenced value of the Au work function (≈5.1 eV), the work functions of non-treated ML-MoS 2 and proton-irradiated ML-MoS 2 with a proton beam flux of 1 × 10 14 protons/cm 2 were determined to be 5.031 eV and 4.992 eV, respectively. The decrease of the work function of the MoS 2 with increased proton beam flux is due to the defect formation induced by proton irradiation. We suggest the possibility of engineering the surface potential and electronic properties of ML-MoS 2 through controlling proton irradiation conditions. [ABSTRACT FROM AUTHOR]

One-dimensional ZnO nanorods were grown vertically on a (100) Si substrate using a vapor phase transport method. Following the fabrication of ZnO nanorods, Si layers were deposited by rapid thermal chemical vapor deposition (RTCVD) directly on the ZnO nanorod/Si (100) substrate. Field emission scanning electron microscopy revealed that a Si/ZnO nanorod coaxial heterostructure were synthesized vertically oriented along the (002) plane on a Si substrate. X-ray diffraction, Energy dispersive X-ray and Raman spectroscopy revealed that the ZnO nanorods were single crystals with a hexagonal structure, and grew with a c-axis orientation perpendicular to the Si substrate, whereas the Si layer was poly-silicon with cubic structure. These results demonstrated the Si/ZnO nanorod coaxial heterostructure were synthesized successfully on a (100) Si substrate and the ZnO nanorod enables the synthesis of a vertically grown well-aligned Si/ZnO coaxial nanorod heterostructure. [ABSTRACT FROM AUTHOR]

Abstract: The p-type InP:Be/Mn/InMnP:Be triple epilayers were prepared using MBE to increase T c (>300 K) by preventing MnO2. After milling 1–3 nm of epilayers thickness from the top surface, the transmission electron microscopy (TEM) and X-ray diffraction (XRD) revealed no MnO2 and precipitates, and TEM and XRD results coincide with results of ferromagnetism. The enhanced ferromagnetic transition at >300 K corresponds to InMnP:Be. The increased ferromagnetic coupling without MnO2 is considered to originate from the increased p–d hybridation. These results demonstrate that InP-based ferromagnetic semiconductor layers having enhanced ferromagnetism can be formed by above process. [Copyright &y& Elsevier]

Abstract: We investigated the carrier transition properties of the GaN/InGaN/GaN single quantum well bounded by AlGaN barriers. In order to confirm the carrier transition coming from the single quantum well, the single quantum well layer was etched by reactive ion etching method. The structural property of the samples was characterized by high resolution X-ray diffraction measurements. In micro-photoluminescence measurements, it is clearly shown that the donor bound exciton transition of the single quantum well sample was redshifted compared to the etched one due to strain. Moreover, a lot of peaks were observed below the GaN band gap energy due to carrier localization in the InGaN/GaN single quantum well, including carrier localization center and quantum confined states. The excitation power dependence and time resolved photoluminescence spectra were investigated to characterize the optical transition of the single quantum well. [Copyright &y& Elsevier]