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PACS. 73.60 -Electronic properties of thin films. PACS. 72.20P -Thermoelectric effects. PACS. 73.40G -Tunnelling: general.Abstract. -The thermopower of a quantum dot, defmed in the two-dimensional electron gas in a GaAs-Alj-Ga! _ ^As heterostructure, is investigated using a current heating technique. At lattice temperatures k^T much smaller than the charging energy e 2 /C, and at small heating currents, sawtoohlike thermopower oscillations are observed äs a function of gate voltage, in agreement with a recent theory. In addition, a remarkable sign reversal of the amplitude of the thermopower oscillations is found in the non-linear regime at large heating currents.Single-electron tunnelling [1] is the dominant mechanism governing the transport properties of a quantum dot that is weakly coupled to reservoirs by tunnel barriers. At temperatures T such that k B T«e 2 /C, with C the capacitance of the dot, it leads the Coulomb-blockade oscillations in the conductance äs a function of the voltage applied to a capacitively coupled gate electrode [2]. Whereas the conductance has been studied extensively, the thermo-electric properties of a quantum dot remain essentially unexplored. Amman et al. have studied theoretically the role of Coulomb interactions on thermo-electric effects in a single mesoscopic tunnel junction, and have used their results to Interpret the thermopower of granulär thin bismuth films [3]. Recently, a theory was developed for the thermopower of a quantum dot in the Coulomb-blockade regime [4]. This theory predicts sawtoothlike oscillations in the thermopower äs a function of the Fermi energy in the reservoirs, with an amplitude that is determined by the charging energy and temperature only.Here, we present an experimental study of the thermo-electric properties of a quantum dot, using the current-heating technique applied previously to study the thermovoltage across a quantum point-contact [5]. At low lattice temperatures and small heating currents,

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Indium nitride (InN) nanowire synthesis using indium (In) vapor transport in a dissociated ammonia environment (reactive vapor transport) is studied in detail to understand the nucleation and growth mechanisms involved with the so-called "self-catalysis" schemes. The results show that the nucleation of InN crystal occurs first on the substrate. Later, In droplets are formed on top of the InN crystals because of selective wetting of In onto InN crystals. Further growth via liquid-phase epitaxy through In droplets leads the growth in one dimension (1D), resulting in the formation of InN nanowires. The details about the nucleation and growth aspects within these self-catalysis schemes are rationalized further by demonstrating the growth of heteroepitaxially oriented nanowire arrays on single-crystal substrates and "tree-like" morphologies on a variety of substrates. However, the direct nitridation of In droplets using dissociated ammonia results in the spontaneous nucleation and basal growth of nanowires directly from the In melt surface, which is quite different from the above-mentioned nucleation mechanism with the reactive vapor transport case. The InN nanowires exhibit a band gap of 0.8 eV, whereas the mixed phase of InN and In(2)O(3) nanowires exhibit a peak at approximately 1.9 eV in addition to that at 0.8 eV.