Nilesh Barange

Temperature dependent dielectric function and the E0 critical points of hexagonal GaN from 30 to 690 K

The complex dielectric function ɛ and the E0 excitonic and band-edge critical-point structures of hexagonal GaN are reported for temperatures from 30 to 690 K and energies from 0.74 to 6.42 eV, obtained by rotating-compensator spectroscopic ellipsometry on a 1.9 μm thick GaN film deposited on a c-plane (0001) sapphire substrate by molecular beam epitaxy. Direct inversion and B-splines in a multilayer-structure calculation were used to extract the optical properties of the film from the measured pseudodielectric function ⟨ɛ⟩. At low temperature sharp E0 excitonic and critical-point interband transitions are separately observed. Their temperature dependences were determined by fitting the data to the empirical Varshni relation and the phenomenological expression that contains the Bose-Einstein statistical factor.

Temperature dependence of the critical points of monolayer MoS2 by ellipsometry

ABSTRACT We report the complex pseudodielectric function of molybdenum disulfide (MoS2) monolayers for energies from 1.40 to 6.42 eV and temperatures from 35 to 350 K. MoS2 was grown as a continuous monolayer on a SiO2/Si substrate in a two zone hot-wall furnace using a catalyst-free chemical vapor growth process. The monolayer was then transferred onto a sapphire substrate. We investigated the optical properties of MoS2 using a dual-rotating-compensator ellipsometer with the sample in ultrahigh vacuum to prevent degradation and to minimize condensation artifacts in the data at low sample temperatures. Critical-point (CP) energies were determined using numerically calculated second energy derivatives of the spectra. At low temperature, we observed a splitting of A-excitonic peak. This identifies the bound excitonic states, including negatively charged excitons, trion states in monolayer MoS2. Splitting of the B-excitonic peak is also indicated. Blue shifts of the CP energies and enhanced structures with reduced electron–phonon interaction are observed as the temperature is lowered. The temperature dependences of the CP energies were fit to a phenomenological expression that contains the Bose–Einstein statistical factor and the temperature coefficient.

Interband transitions and dielectric functions of InGaSb alloys

We report pseudodielectric functions of In1−xGaxSb ternary alloy films from 1.5 to 6.0 eV determined by spectroscopic ellipsometry. Artifacts were minimized by real-time assessment of overlayer removal, leading to accurate representations of the bulk dielectric responses of these materials. Critical-point (CP) energies were obtained from numerically calculated second energy derivatives, and their Brillouin-zone origins identified by band-structure calculations. The E2′ and E2 + Δ2 CP energies cross with increasing In content as a result of increasing spin-orbit splitting Δ2.

Parametrization of the Optical Constants of AlAs x Sb 1-x Alloys in the Range 0.74-6.0 eV

We report parameters that allow the dielectric functions

Alternative Patterning Process for Realization of Large-Area, Full-Color, Active Quantum Dot Display

{\varepsilon}={\varepsilon}_1+i{\varepsilon}_2

Simultaneous Improvement of Charge Generation and Extraction in Colloidal Quantum Dot Photovoltaics Through Optical Management

of

Dielectric function and critical points of AlP determined by spectroscopic ellipsometry

AlAs_xSb_{1-x}

Graphene Quantum Rings Doped PEDOT:PSS Based Composite Layer for Efficient Performance of Optoelectronic Devices

alloys to be calculated analytically over the entire composition range

Temperature dependence of the dielectric function and critical-point energies of InAs

0{\leq}x{\leq}1

Effect of the Ga Ratio on the Dielectric Function of Solution-processed InGaZnO Films

in the spectral energy range from 0.74 to 6.0 eV by using the dielectric function parametric model (DFPM). The