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The authors report the results of an experimental investigation of the low-frequency noise in the double-gate graphene transistors. The back-gate graphene devices were modified via addition of the top gate separated by ∼20 nm of HfO2 from the single-layer graphene channels. The measurements revealed low flicker noise levels with the normalized noise spectral density close to 1/f (f is the frequency) and Hooge parameter αH≈2×10−3. The analysis of noise spectral density dependence on the top and bottom gate biases helped to elucidate the noise sources in these devices. The obtained results are important for graphene electronic and sensor applications.

The authors show that the ordered three-dimensional arrays of quantum dots, i.e., quantum dot supracrystals, can be used to implement the intermediate-band solar cell with the efficiency exceeding the Shockley-Queisser limit for a single junction cell. The strong electron wave function overlap resulting in minibands formation allows one to tune the band structure and enhance the light absorption and carrier transport. A first-principles semianalytical approach was used to determine the optimum dimensions of the quantum dots and the interdot spacing to achieve a maximum efficiency in the InAs 0.9 N 0.1 / GaAs 0.98 Sb 0.02 quantum dot supracrystal photovoltaic cells.

ITO thin films were deposited on glass substrates by d.c. magnetron sputtering with varied oxygen flow rates. It was found that the optical absorption decreases and optical absorption edge has blue shifts with the increasing oxygen flow rate. Oxygen vacancy concentration was characterized and analyzed by XPS. It is shown that the oxygen vacancy concentration increases with oxygen flow rates, which is a different observation from the current understanding. The energy band structures associated with different vacancy concentrations of ITO were calculated using the first-principle based on density functional theory. The calculation results show that the increase of oxygen vacancies induces the increase of bands below Fermi level as well as the presence of a second band gap, which accounts for effects of the oxygen vacancies on the blue shifts.