Fatemeh Dehghan Nayeri - Academia.edu (original) (raw)

Uploads

Papers by Fatemeh Dehghan Nayeri

Iranian Journal of Chemistry & Chemical Engineering-international English Edition, Sep 1, 2007

Cu-Mo and Cu-Ti contact structures were fabricated on multi-crystalline silicon substrates to pro... more Cu-Mo and Cu-Ti contact structures were fabricated on multi-crystalline silicon substrates to provide a low resistance ohmic contact. Deposition steps are done in an excellent vacuum chamber by means of electron beam evaporation and samples are then annealed for the realization of an efficient alloy layer. The effects of process parameters such as film thickness, annealing duration and temperature on the contact quality have been investigated and optimized for achieving the best special contact resistivity. The specific contact resistance obtained for Cu-Mo and Cu-Ti structures were 8.58×10-6 Ω-cm 2 and 9.72×10-6 Ω-cm 2 , respectively. Finally, between the two proposed structures a comparison has been made which is resulted in the selection of Cu-Mo contact as the better structure due to its less resistance and better adhesion to the substrate.

Journal of Physics D: Applied Physics, 2018

Core–shell heterostructures of ZnO-NWs/CdTe-NPs were fabricated through covering ZnO-NWs arrays u... more Core–shell heterostructures of ZnO-NWs/CdTe-NPs were fabricated through covering ZnO-NWs arrays using CdTe-NPs and the room temperature RF magnetron sputtering method. The influence of different CdTe-NPs deposition time (5, 20, 40 and 60 min) on the physical properties of core–shell heterostructures were investigated. In order to achieve the highest coverage level and a wide range of optical absorption at a visible range for a ZnO-NWs/CdTe-NPs (60 min) array, FTO/ZnO-NWs/CdTe-NPs (60 min)/Ni/Au core–shell solar cells were used. Solar cell fabrication was performed by soaking the samples in a saturated CdCl2 solution in methanol and a post-annealing treatment at 400 °C for 1 h in air which led to grain growth, the passivation of deep level defects, and the decrease of stacking faults. Short-circuit current and power conversion efficiency of the fabricated cell under illumination with visible light AM1.5 (100 mW cm−2) were 13.3 mA cm−2 and 3.41%, respectively. It was found that introducing a thin interfacial layer of CdSe to the configuration (FTO/ZnO-NWs/CdSe (10 nm)/CdTe-NPs (60 min)/Ni/Au) led to a 5.58% enhancement of photovoltaic performance of the solar cell (20.9 mA cm−2), which is 63.6% more than that of the same configuration without CdSe.

MRS Proceedings, 2005

A novel plasma hydrogenation method for the fabrication of nano-crystalline structures of silicon... more A novel plasma hydrogenation method for the fabrication of nano-crystalline structures of silicon as well as the photoluminescence and structural properties of these porous structures is presented. We have observed that the hydrogenation process followed by an annealing treatment results in the formation of nano-crystalline silicon structures where increased temperatures during hydrogenation reduces the grain size. Furthermore, by increasing the time of the hydrogenation process, the density of the silicon grains is increased.Photoluminescence (PL) spectroscopy demonstrated the presence of a direct gap in the visible light range where materials with a smaller grain size emitted light at lower wavelengths, and a higher density of grains resulted in higher amplitudes in the PL spectrum. TEM and SEM characterization of these samples and the structure-emission relationship are also presented.

Sensors and Actuators B: Chemical, 2016

Recently, humidity sensors due to their broad applications in meteorology, health science, food s... more Recently, humidity sensors due to their broad applications in meteorology, health science, food science, and agriculture have been under extensive investigation. We report fabrication and characterization of high sensitivity capacitive humidity sensors based on ZnO nanorods. ZnO nanorods have been grown by means of chemical bath deposition. We have observed that by changing the seed layer thickness, nanorods with different aspect ratios and densities could be achieved. Furthermore, it is demonstrated that decreasing the density of nanorods has a positive effect on the response of the sensor. Moreover, an equivalent circuit model is proposed to explain the sensing mechanism. The devices were also simulated with COMSOL Multiphysics and a very good agreement with experimental data was observed. Finally a solution for increasing the sensitivity of the sensors is proposed.

In this paper, we describe a cost-effective and efficient approach for the large-scale synthesis ... more In this paper, we describe a cost-effective and efficient approach for the large-scale synthesis of heterojunctions between ZnO NRs and MWCNTs. Our work represents a new type of heterostructure with many benefits. The effects of precursor concentration, growth temperature and time on nanorods morphology on MWCNT were investigated systematically. It is demonstrated that the controllable growth of ZnO nanorods on MWCNT can be realized by readily adjusting the preparation parameters.

Journal of Alloys and Compounds, 2015

High aspect ratio zinc oxide (ZnO) nanotubes (NT) were synthesized based on a two-steps approach.... more High aspect ratio zinc oxide (ZnO) nanotubes (NT) were synthesized based on a two-steps approach. In the first step, ZnO nanorod (NR) arrays were prepared by chemical bath deposition from an aqueous of zinc nitrate. In the second step, the cores of ZnO NRs were carved selectively in a KCl solution, resulting in the formation of a tubular structure. The influence of KCL concentration, temperature, and immersion time on the ZnO NT formation process was completely characterized and investigated. 12.5 lm NRs and NTs have been utilized to manufacture dye-sensitized solar cells (DSSCs) and as a result, conversion efficiencies of 1.06% and 2.87% were obtained, respectively. Electrochemical impedance spectroscopy measurements have demonstrated that the NTs could acquire a higher electron lifetime compared to NRs which causes a faster electron collection. The overall improvement in NT-based DSSC performance demonstrates a new approach to enhance the efficiency of dye-sensitized solar cells. Ó 2015 Elsevier B.V. All rights reserved. 2. Materials and methods 2.1. Synthesis of ZnO NT arrays on ITO glass substrate Indium doped tin oxide (ITO) glasses were used as the substrates for the growth of ZnO NRs. Aluminum doped zinc oxide (AZO) seed layer was sputtered on the ITO glass substrate by radio frequency sputtering. The growth solution contained zinc

Materials Science and Engineering: B, 2005

The preparation of porous silicon films by DC-plasma hydrogenation and subsequent annealing of am... more The preparation of porous silicon films by DC-plasma hydrogenation and subsequent annealing of amorphous silicon films on silicon and glass substrates is reported for the first time. The effects of varying plasma power and annealing temperatures have been investigated and characterized by scanning-electron microscopy, transmission-electron microscopy, and photoluminescence. A plasma density of about 5.5W/m2 and hydrogenation-annealing temperatures of about 400°C

Superlattices and Microstructures, 2016

High density vertically aligned ZnO nanowire was coated with CdS nanocrystals of different thickn... more High density vertically aligned ZnO nanowire was coated with CdS nanocrystals of different thicknesses by the RF magnetron sputtering process and applied as photoanode in CdS quantum dot sensitized solar cells. Field emission scanning electron microscopy (FESEM), photoluminescence, and X-Ray diffraction (XRD) were utilized to characterize the samples and study their properties. Results demonstrated that, after dye decoration co-sensitized process, the ZnO/CdS heterostructures showed an overall power conversion efficiency of 2.68%, which is 76.3% improvement over that of pristine ZnO/CdS-QDSSC. Thereby, the QDSSC was assembled with modified ZnO/CdS heterostructures by Dye exhibited high performance.

Experimental Techniques, 2012

Aligned ZnO nanowires (NWs) were synthesized by low-temperature wet chemical bath deposition (CBD... more Aligned ZnO nanowires (NWs) were synthesized by low-temperature wet chemical bath deposition (CBD) technique on indium tin oxide (ITO)-coated glass substrates using c-axis orientated ZnO and AZO (Al-doped ZnO) seed layers through the RF sputtering deposition process under different conditions. The growth direction of ZnO NW was controlled by using the two different seed layers. Results showed single-crystalline structure of the ZnO NWs with the highest peak intensity in (002) crystalline direction. In addition, NWs seeding form AZO layer, grown on ITO coated glass, were vertically aligned and uniformly distributed on the substrate. The effects of precursor concentration, growth temperature, and seed layer on NW morphology were investigated in two different seed layers systematically. The intensity of broad emissions at 500-600 nm emission was observed in room temperature photoluminescence (PL) spectra for samples prepared under optimized parameters. In addition, the green emission intensity of ZnO NWs growth on the ZnO seed layer was much weaker than that of AZO seed layer. The experimental results indicate that the selection of seed layers, precursor concentration, and the growth temperature are key parameters to vertical growth of NWs for the application of nanoscale devices.