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Electrically-inactive arsenic (As) complexes in silicon are investigated using time-of-flight mediumenergy ion scattering spectroscopy. In heavily As-doped Si, the As atoms that are segregated in the Si interface region just below the SiO2 are found to be in interstitial forms (Asi), while the As atoms in the bulk Si region are found to be in the substitutional form (AsSi). Despite the substitutional form of As, most of the As are found to be electrically inactive in the bulk region, and we identify the As to be in the form of a 〈111〉-oriented AsSi-Si-vacancy (AsSi-VSi) complex. The Asi atoms in the interface Si region are found to exist together with Si-interstitial atoms (Sii), suggesting that the Asi atoms in the interface Si region accompany the Sii atoms. [ABSTRACT FROM AUTHOR]

Thermal conductivity of a material is an important physical parameter in electronic and thermal devices, and as the device size shrinks down, its length-dependence becomes unable to be neglected. Even in micrometer scale devices, materials having a long mean free path of phonons, such as crystalline silicon (Si), exhibit a strong length dependence of the thermal conductivities that spans from the ballistic to diffusive thermal transport regime. In this work, through nonequilibrium molecular-dynamics (NEMD) simulations up to 17 μm in length, the lattice thermal conductivities are explicitly calculated for crystalline Si and up to 2 μm for amorphous Si. The Boltzmann transport equation (BTE) is solved within a frequency-dependent relaxation time approximation, and the calculated lattice thermal conductivities in the BTE are found to be in good agreement with the values obtained in the NEMD. The isotopic effects on the length-dependent lattice thermal conductivities are also investigated both in the crystalline and amorphous Si. [ABSTRACT FROM AUTHOR]

The quantitative analysis of mechanism on negative bias illumination stress (NBIS)-induced instability of amorphous indium-tin-zinc-oxide thin-film transistor (TFT) was suggested along with the effect of equivalent oxide thickness (EOT) of gate insulator. The analysis was implemented through combining the experimentally extracted density of subgap states and the device simulation. During NBIS, it was observed that the thicker EOT causes increase in both the shift of threshold voltage and the variation of subthreshold swing as well as the hump-like feature in a transfer curve. We found that the EOT-dependence of NBIS instability can be clearly explicated with the donor creation model, in which a larger amount of valence band tail states is transformed into either the ionized oxygen vacancy VO2+ or peroxide O22- with the increase of EOT. It was also found that the Vo2+-related extrinsic factor accounts for 80%-92% of the total donor creation taking place in the valence band tail states while the rest is taken by the O22- related intrinsic factor. The ratio of extrinsic factor compared to the total donor creation also increased with the increase of EOT, which could be explained by more prominent oxygen deficiency. The key founding of our work certainly represents that the established model should be considered very effective for analyzing the instability of the post-indium-gallium-zinc-oxide (IGZO) ZnO-based compound semiconductor TFTs with the mobility, which is much higher than those of a-IGZO TFTs [ABSTRACT FROM AUTHOR]

We report the fabrication and characterization of woodpile photonic crystals with up to 12 layers through titania nanoparticle infiltration of a polymer template made by soft lithography. Because the complicated alignment in the conventional layer-by-layer fabrication associated with diamondlike symmetry is replaced by a simple 90° alignment, the fabricated photonic crystal has semicrystalline phase. However, the crystal performs similarly to a perfectly aligned crystal for the light propagation integrated from the surface normal to 30° at the main photonic band gap. [ABSTRACT FROM AUTHOR]

We perform first-principles calculations on metal-HfO2 interfaces in the presence of oxygen vacancies. Pt, Al, Ti, and Ag are considered as electrodes. It is found that oxygen vacancies are strongly attracted to the interface with binding energies of up to several eVs. In addition, the vacancy affinity of interfaces is proportional to the work function of metals, which is understood by the transition level of the vacancy and metal-Hf bonding. Interfacial segregation of vacancies significantly affects effective work functions of p metals. Our results are consistent with flatband shifts in p-type field effect transistors employing high-k dielectrics and metal gates. [ABSTRACT FROM AUTHOR]

Ge nanodots (NDs) for nonvolatile memories (NVMs) have been self-assembled at room temperature (RT) by ion beam sputtering deposition of ultrasmall amount Ge (<72 ML) on SiO2 without postannealing. High-resolution transmission electron microscopy demonstrates the existence of well-defined Ge ND layers with respect to the SiO2/Si interface. As Ge amount increases, the size of NDs increases, while their density decreases. A possible mechanism is proposed to explain the formation of Ge NDs at RT based on simple model calculations. The memory window that is estimated by capacitance-voltage hysteresis increases up to 18.7 V with increasing Ge amount up to 54 ML. The program speed is enhanced by increasing Ge amount and the charge-loss speed in the programed state is slower for larger Ge amount. These NVM properties are very promising in view of device application. [ABSTRACT FROM AUTHOR]

We perform first-principles density-functional calculations to study the stability of donor-pair defects at Si/SiO2 interfaces. For P dopants, individual dopant atoms energetically favor Si lattice sites in the interface region, as compared to bulk Si. When dopant atoms aggregate to the interface region at very high dopant concentrations, dopant segregation occurs in form of electrically deactivating nearest-neighbor donor pairs that comprise two threefold coordinated dopant atoms. Our defect model explains both the redistribution and deactivation of dopant atoms observed at Si/SiO2 interfaces. [ABSTRACT FROM AUTHOR]

We studied the first-order diffracted moiré fringes of transparent multilayered structures comprised of irregularly deformed periodic patterns. By a comparison study of the diffracted moiré fringe pattern and detailed microscopy of the structure, we show that the diffracted moiré fringe can be used as a nondestructive tool to analyze the alignment of multilayered structures. We demonstrate the alignment method for the case of layer-by-layer microstructures using soft lithography. The alignment method yields high contrast of fringes even when the materials being aligned have very weak contrasts. The imaging method of diffracted moiré fringes is a versatile visual tool for the microfabrication of transparent deformable microstructures in layer-by-layer fashion. [ABSTRACT FROM AUTHOR]