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Oxide-based electronics call for low-cost and stable semiconductors to reduce cost and enable long-term operations. Transistors based on Sn show high field-effect mobility but generally exhibit weak stability and difficulty in solution-processed patterning. Here, we report solution-processed tin-gallium-oxide (SnGaO) thin-film transistors (TFTs) for In- and Zn-free electronics. Different from tin oxide, the amorphous SnGaO semiconductor features a wide bandgap of 4.6 eV, can be wet-etched and patterned by photolithography, and exhibits a large on-off ratio and good device stability in TFTs. The films are deposited via a sol-gel process and, in the photoelectron spectra, they exhibit typical signals of Sn4+ and Ga3+, which act as the electron provider and suppresser, respectively. By varying the elemental ratios, the average field-effect mobility could be well controlled over a wide range from 0.66 to 9.82 cm2/V s, the maximum mobility can reach 12 cm2/V s, and the on/off ratio is above 106. The devices exhibited good stability for positive and negative bias stressing as well as with illumination, probably attributed to Ga-O bonds which are stronger than the weak Zn-O bonds. The presented studies may provide useful information to understand thin-film devices based on tin oxide and gallium oxide semiconductors.

Size self-scaling effect in stacked InAs/In0.52Al0.48As nanowires on InP substrates is revealed, i.e., the base width and height of the InAs nanowires have clear proportional dependence on thickness of the InAlAs spacer layer used in different samples. The photoluminescence wavelength from different samples, which varies between 1.3 and 1.9 mum, is also found closely correlated to the size self-scaling effect. This phenomenon can be well explained in the context of formation mechanism and growth features of the InAs/InAlAs nanowire arrays. The finding illustrates a degree of freedom to control the structural and optical properties of strained self-organized nanostructures. (C) 2004 American Institute of Physics.

Self-organized InAs islands on (001) GaAs grown by molecular beam epitaxy were annealed and characterized with photoluminescence (PL) and transmission electron microscopy (TEM). The PL spectra from the InAs islands demonstrated that annealing resulted in a blueshift in peak energy, a reduction in intensity, and a narrower linewidth in the PL peak. In addition, the TEM analysis revealed the relaxation of strain in some InAs islands with the introduction of the network of 90° dislocations. The correlation between the changes in the PL spectra and the relaxation of strain in InAs islands was discussed.

The extreme reduction of the thermal conductivity by defects and folds in carbon nanocoils (CNCs) are first demonstrated using nonequilibrium molecular dynamics simulations. The thermal conductivity for two different defect types with five different folds in the CNCs is extensively studied and the maximum reduction can be up to 70% at both room temperature and 600 K by comparison of the corresponding straight single-walled carbon nanotubes. We reveal that the phonon scattering by coupled defects and folds can govern the reduction of the thermal conductivity by calculating phonon polarization vectors.

By using a combination of the first-principles density functional theory and nonequilibrium Green's function for electron and phonon transport, we investigate the thermoelectric properties of silicon-germanium superlattice nanowires (NWs). Our results show that introducing superlattice structures always increases thermoelectric figure of merit, ZT, which depends on the periodic length of the superlattice NWs. For n-type superlattice NWs, the achievable maximum ZT is 4.7, which is 5-fold increase as compared to the equivalent pristine silicon NWs. For p-type wires, the achieved maximum ZT is 2.74, which is 4.6-fold increase as compared to the pristine silicon NWs.

The lattice dynamics properties are investigated for twisting bilayer graphene. There are big jumps for the inter-layer potential at twisting angle θ=0° and 60°, implying the stability of Bernal-stacking and the instability of AA-stacking structures, while a long platform in [8,55]° indicates the ease of twisting bilayer graphene in this wide angle range. Significant frequency shifts are observed for the z breathing mode around θ=0° and 60°, while the frequency is a constant in a wide range [8,55]°. Using the z breathing mode, a mechanical nanoresonator is proposed to operate on a robust resonant frequency in terahertz range.

In this letter, a nanomachined optical logic gate using optical gradient force is demonstrated. The device consists of a partially free-hanging silicon double-ring resonator developed by the nano-electro-mechanical system technology. The logic NOR gate function is demonstrated at 20 Mb/s with a high extinction ratio of about 21.3 dB. This proposed NOR gate has the advantages of low power consumption (∼0.5 mW), highly compacted size (40 μm × 45 μm), and easy batch fabrication which has potential applications in silicon-photonic integration for digital signal processing. Published version

We study thermal transport in folded graphene nanoribbons using molecular dynamics simulations and the non-equilibrium Green's function method. It is found that the thermal conductivity of flat graphene nanoribbons can be modulated by folding and changing interlayer couplings. The analysis of transmission reveals that the reduction of thermal conductivity is due to scattering of low frequency phonons by the folds. Our results suggest that folding can be utilized in the modulation of thermal transport properties in graphene and other two dimensional materials., published in Applied Physics Letters 2012

The minimum thermal conductance versus supercell size ($d_{s}$) is revealed in graphene and boron nitride superlattice with $d_{s}$ far below the phonon mean free path. The minimum value is reached at a constant ratio of $d_{s}/L\approx 5%$, where $L$ is the total length of the superlattice; thus the minimum point of $d_{s}$ depends on $L$. The phenomenon is attributed to the localization property and the number of confined modes in the superlattice. With the increase of $d_{s}$, the localization of the confined mode is enhanced while the number of confined modes decreases, which directly results in the minimum thermal conductance., Comment: accepted by APL

The effect of GaAs cap layer with different thicknesses in the GaAs/In0.3Ga0.7As/GaAs heterostructure on misfit dislocation is investigated with transmission electron microscopy, and it is found that lines of misfit dislocation break up and move out of the structure when the GaAs cap layer thickness exceeds a certain amount. The breaking up and moving out of misfit dislocations, initially confined in the (001) substrate/InGaAs epilayer interface, occur mainly along the [110] direction on the interface in the structure.

Wafers of float zone Si grown in hydrogen (Si[H]) were annealed at various temperatures in the range of 300–750 °C before irradiation with 5 MeV electrons. It was found that hydrogen‐related deep levels were no longer observed, when the preannealing temperature was above 500 °C (450 °C) in the case of irradiated n‐type Si[H] (p‐type Si[H]) samples. Similarly, the convergence of annealing temperatures of different irradiation defects towards a common temperature normally observed in Si[H] was no longer observed, if the Si[H] sample had been annealed at or above 550 °C. A dynamic model is proposed to explain the experimental results.