Sharif Digital Repository

A Gate All Around Nanowire Transistor (GAA NWT) which employs source heterojunction and strained channel is proposed which improves device characteristics. A quantum mechanical transport approach based on nonequilibrium Green's function (NEGF) method in the frame work of effective mass theory is employed in this analysis. We evaluate the variation of the threshold voltage, the subthreshold slope, ON and OFF state currents when channel length decreases. It is shown that the source heterojunction strained channel GAA NWT gives high performance transistors values of the scaled transconductance and ON current that are greater than conventional silicon GAA NWT. Furthermore, comparison of... 

Herein, a solution-processed, bottom-up-fabricated, nanowire network electrode is developed. This electrode features a ZnO template which is converted into locally connected, infiltratable, TiO2 nanowires. This new electrode is used to build a depleted bulk heterojunction solar cell employing hybrid-passivated colloidal quantum dots. The new electrode allows the application of a thicker, and thus more light-absorbing, colloidal quantum dot active layer, from which charge extraction of an efficiency comparable to that obtained from a thinner, planar device could be obtained  

A new magnetic composite was synthesized by integration of ZnFe2O4 and MIL-53(Fe) micro-rods by a solvothermal method. This composite served as a heterogeneous catalyst to overcome the high electron-hole recombination rates of ZnFe2O4 and to enhance the degradation of Direct Red 23 under visible light irradiation. Different analytical techniques, including XRD, FTIR, SEM, DRS, VSM, and PL, were employed to characterize the synthesized heterojunction nanocomposite and to evaluate its photocatalytic activity. The ZnFe2O4/MIL-53(Fe)/Vis-light system resulted in significantly higher dye degradation as compared with pristine ZnFe2O4 and MIL-53(Fe) semiconductors at the optimum pH of 3.1 and... 

Visible light-active BiOCl/BiVO4/mordenite and Ag/BiOCl/BiVO4 nanocomposite with a p–n heterojunction structure were prepared. Mordenite nanocrystals were synthesised using the hydrothermal method. Deposition and reduction methods were utilised to modify the Zeolite surface. The photocatalytic activities of the heterojunctions were investigated by scanning the change of Acid blue 92 (AB92) concentration under visible irradiation. The nanocomposites demonstrated improved efficiency for dye photodegradation. The activities are due to strong oxidative ability and efficient charge separation and transfer through the BiOCl/BiVO4 p–n junction. The photogenerated electron-holes react with species... 

Visible light-active BiOCl/BiVO4/mordenite and Ag/BiOCl/BiVO4 nanocomposite with a p–n heterojunction structure were prepared. Mordenite nanocrystals were synthesised using the hydrothermal method. Deposition and reduction methods were utilised to modify the Zeolite surface. The photocatalytic activities of the heterojunctions were investigated by scanning the change of Acid blue 92 (AB92) concentration under visible irradiation. The nanocomposites demonstrated improved efficiency for dye photodegradation. The activities are due to strong oxidative ability and efficient charge separation and transfer through the BiOCl/BiVO4 p–n junction. The photogenerated electron-holes react with species... 

A solution-processed, bottom-up nanowire network electrode is developed and employed in a bulk heterojunction colloidal quantum dot solar cell. The electrode features a ZnO template which is converted into locally connected, infi ltratable TiO2 nanowires. The new electrode allows the application of a thicker light absorbing fi lm without compromising the charge extraction, as reported by Edward H. Sargent, Ghassan Jabbour, and co-workers on page 1769. The frontispiece shows schematically the electrode shape and the resultant device architecture  

Abstract A visible-light-active Ag3PO4/BiPO4 nanocomposite with a p-n heterojunction structure was fabricated via a co-precipitation hydrothermal process using 2-hydroxylethylammonium formate (RTIL) as a room-temperature ionic liquid. The resulting catalysts were characterized by various techniques. The photocatalytic activity of the photocatalysts was evaluated by the photodegradation of phthalocyanine Reactive Blue 21 (RB21) under both visible and UV light irradiations. The results reveal that the heterojunction composite prepared in RTIL noticeably exhibited an improvement in both efficiency and rate of RB21 photodegradation in comparison with pure Ag3PO4 and BiPO4. The enhanced... 

Carbon nanotubes (CNT) have unique electronic properties and remarkable optical properties. Despite of on layer thickness of CNTs, it has able to absorb photons from visible to far infrared and terahertz. These unique properties lets to create heterojunction devices by semiconductor/CNTs or metal/CNTs junctions e.g. photodiodes, sensor and heterojunction solar cell. The CNTs can play the role of a heterojunction component for charge separation as a high conductive network for charge transport and as a transparent electrode for light illumination and charge collection. The main objective of the present article is to establish a relation between interface recombination and the characteristics... 

Hybrid nanostructures combining semiconductor quantum dots and graphene are attracting increasing attention because of their optoelectronic properties promising for photovoltaic applications. We present a hot-injection synthesis of a colloidal nanostructure which we define as quasi core/shell PbS/graphene quantum dots due to the incomplete passivation of PbS surfaces with an ultrathin layer of graphene. Simulation by density functional theory of a prototypical model of a nonstoichiometric Pb-rich core (400 atoms) coated by graphene (20 atoms for each graphene sheet) indicates the possibility of surface passivation of (111) planes of PbS with graphene resulting in a decrease in trap states... 

Enhancing the photoresponse of single-layered semiconductor materials is a challenge for high-performance photodetectors due to atomically thickness and limited quantum efficiency of these devices. Band engineering in heterostructure of transition metal chalcogenides (TMDs) can sort out part of this challenge. Here, we address this issue by utilizing the plasmonics phenomenon to enrich the optoelectronics property of the WSe2/MoS2 heterojunction and further enhancement of photoresponse. The introduced approach presents a contamination-free, tunable and efficient way to improve light interactions with heterojunction devices. The results showed a 3600-fold enhancement in photoresponsivity and... 

Titanium oxide (TiO2)-based photodetectors were fabricated using a thermal oxidation technique. The effect of two different annealing temperatures on morphology, structure, and I-V characteristics has been investigated. TiO2/Si heterostructure exhibited diode-like rectifying I-V behavior both in dark and under illumination. Dependence in photoresponse on annealing temperature was observed that was related to effective surface area of quasi-one-dimensional TiO2 nanostructures. Fabricated TiO2/Si diodes in 850 °C as the lower annealing temperature showed higher responsivity and sensitivity compared with grown ones in 950 °C (R850 °C/R950 °C ∼ 5 and S850 °C/S950 °C ∼ 1.6). Rather good... 

In this paper, we present a computational study on the electrical behaviour of self-switching transistors (SSTs) based on InGaAs/InP heterojunction. Our simulation is based on the solution of Poisson and Schrodinger equations self-consistently by using Finite Element Method (FEM). By using this method, electrical characteristics of device, such as (Formula presented.) ratio, subthreshold swing, and intrinsic gate-delay time are investigated. Also, the effects of geometrical variations on the electrical parameters of SSTs are simulated. We show that appropriate design of the device allows current modulation exceeding (Formula presented.) at room temperature. © 2021 Informa UK Limited, trading... 

Abstract We report the well-controlled preparation of WS2 nanosheets-CdS nanoparticle heterojunction for photoelectrochemical (PEC) water splitting application. The WS2 nanosheets with an average thickness of ~5 nm and lateral dimensions of ~200 nm were synthesized via liquid phase exfoliation of bulk WS2 in water/ethanol solution, followed by deposition onto ITO substrate via electrophoretic method. CdS nanoparticles were grown via facile successive ion layer absorption and reaction (SILAR) method. Using these two well-controlled methods, CdS/WS2/ITO and WS2/CdS/ITO systems were fabricated. The loading of WS2 nanosheets was... 

The conventional solar cell architectures include a p-n junction of c-Si sandwiched by rear and front contacts. The conventional approach features a complex as well as expensive procedure. Here, we propose a new architecture for p-n heterojunction solar cells prepared by a simple and cost-effective procedure. In this regard, (1) a silicon wafer underwent surface treatment through electrochemical anodization. To prepare a stick junction, (2) photoactive TiO2 nanoparticles were deposited over the porous layer by electrophoretic technique. Finally, (3) indium tin oxide (ITO) was sputtered. During the fabrication steps, we examined various anodization times ranging from 6 to 12 min to study the... 

Two-dimensional semiconductor materials can be combined with conventional silicon-based technology and sort out part of the future challenges in semiconductor technologies due to their novel electrical and optical properties. Here, we exploit the optoelectronics property of the silicon/SnS2 heterojunction and present a new class of backward diodes using a straightforward fabrication method. The results indicate an efficient device with fast photoresponse time (5-10 μs), high photoresponsivity (3740 AW-1), and high quantum efficiency (490%). We discuss device behavior by considering the band-to-band tunneling model and band bending characteristics of the heterostructure. This device structure... 

In this study, we synthesized novel visible light photocatalyst MIL-88A/BiOI using depositing BiOI particles on the surface of a metal–organic framework (MIL-88A). Photocatalytic application of binary composite MIL-88A/BiOI was obtained by discoloration of Methylene Blue (MB) and Acid Blue 92 (AB92) in aqueous solution under visible light source. The photodegradation experiments for treating organic dyes show that the MIL-88A/BiOI heterojunction structure possess a higher rate for decomposition of dyes due to the decreased aggregation of the BiOI nanoparticles, effective charge carrier separation and the synergistic effect between MIL-88A and BiOI samples as a heterojunction. Also, the... 

TiO2 is a promising photoanode material for photoelectrochemical (PEC) water splitting, but its severe bulk recombination of photogenerated carriers, sluggish oxygen evolution reaction (OER) kinetics and poor visible light response are the main bottleneck problems. Here, the carbon quantum dots (CQDs) modified anatase/rutile TiO2 photoanode (CQDs/A/R-TiO2) was designed by growth of anatase TiO2 nanothorns on rutile TiO2 nanorods and further surface modification of CQDs. The results revealed that the A/R-TiO2 heterojunction significantly suppressed the bulk recombination of photogenerated carriers. With further incorporation of CQDs into A/R-TiO2, dramatical improvement of OER kinetics and... 

In this contribution, spinel MgAl2O4 nanospheres prepared by the combustion method were coupled with thermally-exfoliated g-C3N4 nanosheets (TE-GCN) through an efficient isoelectric point-assisted calcination technique. Physical characteristics of the synthesized nanocomposite were understudied utilizing the XRD, FT-IR, FE-SEM, TEM, BET-BJH, UV–Vis DRS, PL, and EIS analyses. This material was used as a novel nano-photocatalyst for degradation of reactive red 195 (RR195) industrial dye contaminant. Results revealed that, a successful synthesis of a heterojunction between the components of the nanocomposite was achieved. This exhibited an enormously improved electron-hole separation leading to...