Communication: Effect of Oxidation on Excited State Dynamics of Neutral TinO2n-x (n<10, x<4) Clusters

Excited state lifetimes of neutral titanium oxide clusters (TinO2n-x, n < 10, x < 4) were measured using a sequence of 400 nm pump and 800 nm probe femtosecond laser pulses. Despite large differences in electronic properties between the closed shell stoichiometric TinO2n clusters and the suboxide TinO2n-x (x = 1-3) clusters, the transient responses for all clusters contain a fast response of 35 fs followed by a sub-picosecond excited state lifetime. In this non-scalable size regime, subtle changes in the sub-ps lifetimes are attributed to variations in the coordination of Ti atoms and localization of charge carriers following UV photoexcitation. In general, clusters exhibit longer lifetimes with increased size and also with addition of O atoms. This suggests that removal of O atoms develops stronger Ti-Ti interactions as the system transitions from a semiconducting character into a fast metallic electronic relaxation mechanism.

Quantum-dot microlasers based on whispering gallery mode resonators

The subject of this paper is microlasers with the emission spectra determined by the whispering gallery modes. Owing to the total internal reflection of light on the sidewalls, a high Q-factor is achieved until the diameter is comparable to the wavelength. The light emission predominantly occurs in the plane of the structure, which facilitates the microlaser integration with other elements. We focus on microdisk lasers with various types of the In(Ga)As quantum dots (QDs). Deep localization of charge carriers in spatially separated regions suppresses the lateral diffusion and makes it possible to overcome the undesirable effect of non-radiative recombination in deep mesas. Thus, using conventional epitaxial structures and relatively simple post-growth processing methods, it is possible to realize small microlasers capable of operating without temperature stabilization at elevated temperatures. The low sensitivity of QDs to epitaxial and manufacturing defects allows fabricating microlasers using III–V heterostructures grown on silicon.

Профилирование компонент подвижности вблизи гетерограниц тонких пленок кремния

In this paper, we proposed the method for profiling of the components of the effective mobility of charge carriers μeff defined by their scattering by surface phonons and by roughness at the film/insulator interfaces. The method is based on the controlled localization of charge carriers relative to the interface under study due to the coupling effect. The proposed method allows us to independently determine mobility components near different interfaces of films. The use of the proposed method for studying the mobility has allowed us to obtain information on the roughness of the interface and on the structural quality of the ultrathin (1–3-nm) layer of Si near the Si/buried oxide interface.

Charge localization and trapping at surfaces in lead-iodide perovskites: the role of polarons and defects

Separate localization of charge carriers for pristine and flat surfaces. Bulk-like physics of defects for the MAI surface while lower formation energies and deeper energy levels for the PbI2 surface.

Люминесцентные свойства тонких пленок Cd-=SUB=-x-=/SUB=-Zn-=SUB=-1-x-=/SUB=-O

Thin Cd_ x Zn_1 – x O films with a Cd content in the range from zero to 35 at % are synthesized by pulsed laser deposition. A record-breaking solubility limit of 30 at % of Cd in wurtzite-structured Cd_ x Zn_1 – x O thin films is attained. Apart from the exciton peak, additional peaks associated with an inhomogeneous distribution of Cd in the samples are observed in the low-temperature (10 K) photoluminescence spectra of Cd_0.15Zn_0.85O and Cd_0.3Zn_0.7O films. An unsteady ( S -like) temperature dependence of the spectral position of the exciton photoluminescence peak in Cd_ x Zn_1 – x O films is observed. Such a dependence is associated with the effect of the localization of charge carriers.

Influence of Mn Site Substitution on Electrical Resistivity and Magnetoresistance Properties of Rare Earth Manganite

We investigate the effects of Cr, Ru and Sn substitution on electrical resistivity and magnetoresistance property of polycrystalline samples La0.67Sr0.33Mn1-xBxO3(x = 0, 0.05; B= Ru, Cr and Sn) compounds. The value of M-I transition temperature (TP) decreases while resistivity increases with Cr, Ru and Sn substitution, moreover, the largest low-temperature magnetoresistance (MR %) is found at magnetic field dependent (Isotherm), which suggest that the spin-dependent scattering from internal grain regions is also responsible for the low-temperature MR %. Resistivity data have been fitted with the variable range hopping model to estimate the density of state at Fermi level. It was observed that the substitution of various transition metals in the Mn-site leads to a decrease in conductivity of the doped manganite samples, with conduction being controlled by the disorder induced localization of charge carriers.