Rise In Carrier Concentration Research Articles

Enhancement of the thermoelectric performance of (BiSb)2Te3 films by single target sputtering

In this study, (BiSb)2Te3 thin films were deposited onto glass substrates at a temperature of 300 °C, utilizing radio frequency (RF) sputtering across a range of growth conditions. The primary focus of this investigation was to analyzse the effects of varying RF power, chamber gas pressure, and annealing temperature on the thermoelectric properties of the films, deposited by an exclusively-made single target.Notably, it was observed that increasing the annealing temperature significantly boosted both the deposition rate and grain size. Through carefully optimizsing growth conditions and subsequent annealing procedures, it was discerned that thin films cultivated at higher RF power levels exhibited markedly improved electrical conductivity, attributed to a discernible rise in carrier concentration. Furthermore, films generated under the RF power of 37.5 W showed a noteworthy augmentation in the Seebeck coefficient, recording approximately 147 μV/K. This enhancement in Seebeck coefficient correlated with the attainment of the highest power factor, reaching an impressive 220.57 μW/mK2.

Synergistic Optimization of Thermoelectric Performance in SnSe2 through co-doping: Anionic Vacancy Formation and Band Engineering

SnSe2 is a layered crystal structure material that is abundant in the Earth's crust and considered non-toxic. However, its thermoelectric properties are anisotropic due to the differences in its interlayer and intralayer electrical and thermal transport properties. The intrinsically poor thermoelectric performance of SnSe2 can be attributed to its lower electrical transport properties in its pristine condition. To address this, we developed a method involving combined mechanical alloying (MA) and spark plasma sintering (SPS) to synthesize n-type Sn-rich Cu-Br co-doped SnSe2 polycrystals. Optimization of Sn enrichment facilitated superior material selection for subsequent doping. The resulting substitutional doping induced a substantial rise in carrier concentration, leading to improved thermoelectric performance. Notably, the power factor displayed a significant increase, reaching approximately 795 µWm-1K-2 at 765 K through Cu-Br co-doping. Furthermore, density functional theory (DFT) analysis elucidated a reduced bandgap and increased degeneracy within the electronic band structure and density of states, affirming the enhancement of thermoelectric properties in Cu-Br co-doped Sn-rich SnSe2 polycrystals. Finally, a maximum figure of merit (ZT) value of 0.46 was achieved at 765 K for the Sn0.985Cu0.015Se1.92Br0.03 sample, perpendicular to the SPS pressing direction, which was nearly threefold higher than the pure SnSe1.95. This compelling outcome highlights the improved thermoelectric performance of the co-doped SnSe2 polycrystals.

Influence of polylactic acid and polycaprolactone on dissolution characteristics of ansamycin-loaded polymeric nanoparticles: An unsatisfied attempt for drug release profile

Objectives: The purpose of the current examination was to establish a polymeric nanoparticle (NP) to supply Ansamycin to the central nervous system by improving blood–brain barrier permeability for bacterial meningitis, by emulsification solvent diffusion technique with numerous hydrophilic carriers. Materials and Methods: The polymeric NPs were prepared by emulsification solvent diffusion technique making use of Polylactic acid (PLA) as well as Polycaprolactone (PCL). Physical mixtures of drug with above-mentioned polymers were likewise prepared. The formulations were examined for Fourier-transform infrared spectroscopy and as well as differential scanning calorimetry (DSC), particle size, and also in vitro dissolution. Similarity factor (f2) was determined for the comparison between dissolution of pure drug and also drug polymer physical mixtures with NPs. Results: Phase solubility researches showed linear increase in the drug solubility with rise in carrier concentration. In vitro release studies disclosed that dissolution quality of Ansamycin was not satisfactory with PLA and also PCL for the release quality of the Ansamycin from the formulation. Nanoformulation of Ansamycin with PLA and also PCL displayed inadequaterate and extent of dissolution. Optimized batches of nano formulations of both the carriers were identified by the Fourier-transform infrared spectroscopy and also DSC evaluation, which suggested existence of interactions between ansamycin and carriers. Conclusions: PLA as well as PCL are not the appropriate polymers to serve as a carrier to deliver Ansamcyin.

Electrical and optical properties of the specimens with graphene quantum dots prepared by different number of wet transfer

Graphene quantum dots (GQDs) are grown on the copper foil substrate by the chemical vapor deposition (CVD) synthesis. 1–3 wet transfer numbers are then used in the preparations of the GQDs/glass substrate in order to improve the density and uniformity of GQDs via the stacking of multiple layers. The CH4 input time, flow rate, and the number of wet transfer are determined to obtain the optimum conditions in electrical (resistivity) and optical (transmittance) properties. The multilayered graphene is characteristically close to the graphite-like material. The G-band peak intensity in Raman analyses is varied proportional to the density of GQDs. Increasing the wet transfer number can lead to increases in the mean diameter of GQDs and the amount of oxygen vacancies, thus resulting in the rise of carrier concentration and the lowering of carrier mobility. The resistivity varying with the wet transfer number is inversely proportional to the density of GQDs. A bandgap reduction can bring in the lowerings of photoluminescence peak intensities. The specimen with 2 wet transfers has the lowest resistivity and the second highest transmittance of these specimens. GQDs can bring in a significant reduction of resistivity compared to the same substrate without GQD.

Effect of 60Co γ-irradiation on the nature of electronic transport in heavily doped n-type GaN based Schottky photodetectors

GaN Schottky photodetectors are fabricated on heavily doped n-type GaN epitaxial layers grown by the hydride vapour phase epitaxy technique. The effect of 60Co γ-radiation on the electronic transport in GaN epilayers and Schottky detectors is studied. In contrast to earlier observations, a steady rise in the carrier concentration with increasing irradiation dose is clearly seen. By considering a two layer model, the contribution of interfacial dislocations in carrier transport is isolated from that of the bulk layer for both the pristine and irradiated samples. The bulk carrier concentration is fitted by using the charge balance equation which indicates that no new electrically active defects are generated by γ-radiation even at 500 kGy dose. The irradiation induced rise in the bulk carrier concentration is attributed to the activation of native Si impurities that are already present in an electrically inert form in the pristine sample. Further, the rise in interfacial contribution in the carrier concentration is governed by the enhanced rate of formation of nitrogen vacancies by irradiation, which leads to a larger diffusion of oxygen impurities. A large value of the characteristic tunnelling energy for both the pristine and irradiated Au/Ni/GaN Schottky devices confirms that the dislocation-assisted tunnelling dominates the low temperature current transport even after irradiation. The advantage of higher displacement energy and larger bandgap of GaN as compared to GaAs is evident from the change in leakage current after irradiation. Further, a fast recovery of the photoresponse of GaN photodetectors after irradiation signifies their compatibility to operate in high radiation zones. The results presented here are found to be crucial in understanding the interaction of 60Co γ-irradiation with n+-GaN epilayers.

Experimental Study on the Electrical Conductivity of Pyroxene Andesite at High Temperature and High Pressure

The electrical conductivity of pyroxene andesite was in situ measured under conditions of 1.0–2.0 GPa and 673–1073 K using a YJ-3000t multi-anvil press and Solartron-1260 Impedance/Gain-phase analyzer. Experimental results indicate that the electrical conductivities of pyroxene andesite increase with increasing temperature, and the electrical conductivities decrease with the rise of pressure, and the relationship between electrical conductivity (σ) and temperature (T) conforms to an Arrhenius relation within a given pressure and temperature range. When temperature rises up to 873–923 K, the electrical conductivities of pyroxene andesite abruptly increase, and the activation enthalpy increases at this range, which demonstrates that pyroxene andesite starts to dehydrate. By the virtue of the activation enthalpy (0.35–0.42 eV) and the activation volume (−6.75 ± 1.67 cm3/mole) which characterizes the electrical properties of sample after dehydration, we consider that the conduction mechanism is the small polaron conduction before and after dehydration, and that the rise of carrier concentration is the most important reason of increased electrical conductivity.

Rapid transfer of methyl red using calix[6]arene as a carrier in a bulk liquid membrane

Abstract In the present investigation, a calix[6]arene-based derivative ( 1 ) is employed as a selective carrier for the efficient transport of methyl red (MR) through bulk liquid membrane (BLM). Initially, the selectivity of 1 towards MR was confirmed among different dyes, such as methyl green (MG), methyl violate (MV), methylene blue (MB), methyl orange (MO), and eosin gelblich (EG) by liquid–liquid extraction experiments. Furthermore, the effect of the initial MR concentration of salts (NaCl, Na 2 SO 4 , and Na 2 CO 3 ) and of the pH of the acceptor phase were also optimized using liquid–liquid extraction. Afterwards, the influence of basic parameters, such as carrier concentration in membrane phase, type of solvent, and stirring rate on MR transport was determined through BLM. Mass transfer of MR through BLM was analyzed by following the kinetic laws of two consecutive irreversible first-order reactions, and the kinetic parameters ( k 1 , k 2 , R m max , t max , J d max , J a max ) were also calculated. Apparently, increase in membrane entrance ( k 1 ) and exit rate ( k 2 ) constants was accompanied by a rise in carrier concentration under a high stirring rate. In addition, CH 2 Cl 2 proved to be a better solvent than CHCl 3 and CCl 4 . The % transport of MR was 99% across the liquid membrane under optimized conditions. Real textile industrial wastewater samples gave also appreciable results in BLM under optimized conditions.

A study of conduction in the transition zone between homologous and ZnO-rich regions in the In2O3–ZnO system

Indium zinc oxide thin films were deposited by radio-frequency cosputtering and characterized by x-ray photoelectron spectroscopy (XPS), x-ray diffraction, energy dispersion x-ray spectrometry, Hall-effect measurement, and spectrophotometry techniques. All the films have zinc∕(zinc+indium) atomic ratio (define as M ratio) higher than 0.60 and exhibited n-type degenerate semiconductor behavior irrespective of their composition. The conductive films have been observed to have a very wide transmittance window (300–2000nm). An XPS analysis revealed a diminishing oxygen vacancy contribution to carrier concentration with an increase in the M ratio. However, we observed a gradual decrease in carrier concentration until M ratio of 0.79 and then, a significant rise in carrier concentration for M ratio of 0.84, and this was attributed to the replacement of zinc from its lattice position by indium. The XPS studies also revealed asymmetry in zinc 2p3∕2 peak, which might be associated with the structure of this ternary system. The effect of the effective mass on the optical band gap of the films was also observed and discussed further.

Heavily-Doped n+-GaAs with Low Compensation Grown by Atmospheric OMVPE

ABSTRACTAtmospheric OMVPE has been used, with SiH4 as the dopant, to grow n+-GaAs with free-carrier levels upto about 9e18 cm−3. Following a steady rise in carrier concentration with dopant pressure, the carrier concentration is seen to fall rapidly with further doping. Hall-effect and quantitative SIMS data have been used to obtain the distribution of silicon onto donor and acceptor sites. It is seen that there is negligible compensation upto free-carrier levels of about 5e18 cm−3. The mechanism of compensation throughout the doping range is discussed.