Phototransistors based on multilayer MoS(2) crystals are demonstrated with a wider spectral response and higher photoresponsivity than single-layer MoS(2) phototransistors. Multilayer MoS(2) phototransistors further exhibit high room temperature mobilities (>70 cm(2) V(-1) s(-1) ), near-ideal subthreshold swings (~70 mV decade(-1) ), low operating gate biases (<5 V), and negligible shifts in the threshold voltages during illumination.

We report on the discovery of a room-temperature ferromagnetic semiconductor in chalcopyrite (Zn1-xMnx)GeP2 with Tc = 312 K. We have also observed that, at temperatures below 47 K, samples for x = 0.056 and 0.2 show a transition to the antiferromagnetic (AFM) state, so that ferromagnetism is well defined to be present between 47 and 312 K. The observation that the AFM phase is most stable at low temperatures is consistent with the predictions of full-potential linearized augmented plane wave total energy calculations and has consequences for other chalcopyrite materials.

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PACS 71.15. Ap, 75.50.Pp, 75.90.+w We have synthesized MnSnAs 2 single crystals using the vertical temperature gradient solidification method. The crystal structure of MnSnAs 2 is chalcopyrites, which are "genealogically" related to the more familiar tetrahedrally-coordinated zinc-blende materials, with lattice constants of a = 5.794 Å, c = 11.365 Å. Using the experimentally determined lattice constants and crystal structure, we carried out first principles electronic structure calculations, using the full-potential linearized augmented plane wave (FLAPW) method in the local density approximation (LDA). The lowest total energies were observed for the AFM state, indicating that AFM ordering in the system is energetically favored at 0 K. We find that MnSnAs 2 is metallic in the electronic calculation. Interestingly, MnSnAs 2 exhibited ferromagnetism with T C = 328 K.

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