The temperature dependence of the conduction mechanism in thin films of ϳ8 nm diameter silicon nanocrystals is investigated using Al/ Si nanocrystal/ p-Si/ Al diodes. A film thickness of 300 nm is used. From 300 to 200 K, space charge limited current, in the presence of an exponential distribution of trapping states, dominates the conduction mechanism. Using this model, a trap density N t = 2.3 ϫ 10 17 cm −3 and a characteristic trap temperature T t = 1670 K can be extracted. The trap density is within an order of magnitude of the nanocrystal number density, suggesting that most nanocrystals trap single or a few carriers at most.

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We investigate the temperature dependence of conduction in size-controlled silicon nanocrystals. The nanocrystals are ϳ8 nm in diameter, covered by ϳ1.5 nm thick SiO 2 shells. In 300 nm thick films for temperatures T from 30 to 200 K, the conductivity follows a ln͑͒ vs 1 / T 1/2 dependence. This may be associated with either percolation-hopping conductance or Efros-Shklovskii variable range hopping. Assuming hopping sites only on the nanocrystals, the data agree well with the percolation model.

Monolayer transition metal dichalcogenides have recently attracted great interests because the quantum dots embedded in monolayer can serve as optically active single photon emitters. Here, we provide an interpretation of the recombination mechanisms of these quantum emitters through polarization-resolved and magneto-optical spectroscopy at low temperature. Three types of defect-related quantum emitters in monolayer tungsten diselenide (WSe 2 ) are observed, with different exciton g factors of 2.02, 9.36 and unobservable Zeeman shift, respectively. The various magnetic response of the spatially localized excitons strongly indicate that the radiative recombination stems from the different transitions between defect-induced energy levels, valance and conduction bands. Furthermore, the different g factors and zerofield splittings of the three types of emitters strongly show that quantum dots embedded in monolayer have various types of confining potentials for localized excitons, resulting in electron-hole exchange interaction with a range of values in the presence of anisotropy. Our work further sheds light on the recombination mechanisms of defect-related quantum emitters and paves a way toward understanding the role of defects in single photon emitters in atomically thin semiconductors. * xlxu@iphy.ac.cn arXiv:2002.03526v1 [cond-mat.mes-hall]

SnS nanoflakes were synthesized using a solid state reaction method at 600 °C and their gas sensing properties were investigated.