Search

CdSe semiconductor thin films were grown on indium tin oxide (ITO) coated glass substrates by co-electrochemical deposition method. Deposition potential was kept at - 0.95 V vs. Ag/AgCl reference electrode for ten minutes. Deposition electrolyte includes an aqueous solution of 10 mM CdCl2, 20 mM H(2)SeO(3 )as precursors, 200 mM LiCl as complexing agent, and HCl for adjusting of pH. Deposited CdSe thin film was annealed at 500 degrees C for 30 min in air medium. Precursor and annealed CdSe thin films were characterized using a number of techniques, including SEM, EDX, XRD, UV-vis spectroscopy, and electrochemical impedance spectroscopy. SEM studies show that annealing alters the surface of precursor CdSe film from smooth to granular appearance. According to EDX analyses, the ratio of Cd/Se is close to 1.07 and 1.04 for the precursor and annealed CdSe thin film, respectively. XRD analysis shows that each film has polycrystalline structure. Precursor film has only cubic structure of CdSe, while annealed film has hexagonal structure of CdSe and cubic crystal phase of CdO. Optical energy band gap of the as-deposited CdSe film increases from 1.64 to 1.71 eV after annealing due to the mixture of the two phases. Refractive index against wavelength changes between 2.0 and 3.3. Calculations performed by using the data of Mott-Schottky measurements show that precursor CdSe film has 1.72 x 10(16 )cm(-3), while annealed film is of 3.65 x 10(17 )cm(-3 )carrier concentration. The prepared films exhibit n-type semiconductor character. The study reports energy level diagrams of the produced semiconductor CdSe thin films by using the Mott-Schottky and Tauc's approximations. The carrier transport properties in the interface between active CdSe thin film and electrolyte are discussed based on an equivalent electronic circuit simulated to the Nyquist data of the CdSe/electrolyte system.

A broadband optical transparent InGaAs semiconductor layer production of micron thicknesses was produced in only 75 s by thermionic vacuum arc (TVA) method at the first time. The optical and surface properties of the produced layers have been investigated. InGaAs structure is using in electronics and optoelectronics devices. The main advantage of TVA method is its fast deposition rate, without any loss in the quality of the films. Doping is a very simple and fast according to common production methods. InGaAs is an alloy of indium arsenide (InAs) and gallium arsenide (GaAs). InAs with (220) crystallographic direction and GaAs with (024)/(022) crystallographic directions were detected using by XRD analysis. GaAs and InAs are in the cubic and zinc blende crystal system, respectively. According to the transmittance spectra, sample has a broadband transparency in the range of 1000–3300 nm. According to results, defined TVA method for In doping to GaAs is proper fast and friendly method. SCANNING 38:297–302, 2016. © 2015 Wiley Periodicals, Inc. © Wiley Periodicals, Inc.

Nanowires show great promise for use in next generation (bio-)chemical sensing devices because of their high surface to volume ratio enabling efficient modulation of their current by charges or dipoles present at the surface. Here, we present a gas sensing device based on vertical InAs nanowire arrays grown without metal catalyst particles. The nanowires are contacted ohmically in their as-grown locations using an air bridge construction, leaving the nanowire surface free for gas adsorption. Noise measurements were performed to determine the measurement resolution for gas detection. The bare devices show sensitivity to NO2 concentrations well below 75 ppb at room temperature. We furthermore find that these nanowires can be functionalized with metalloporphyrins resulting in sensitivity to both NO2 and NO concentrations below 75 ppb.

Ferroelectric polarization switching of poly(vinylidene difluoride-trifluoroethylene) is investigated in different thin-film device structures, ranging from simple capacitors to dual-gate thin-film transistors (TFT). Indium gallium zinc oxide, a high mobility amorphous oxide material, is used as semiconductor. We find that the ferroelectric can be polarized in both directions in the metal-ferroelectric-semiconductor (MFS) structure and in the dual-gate TFT under certain biasing conditions, but not in the single-gate thin-film transistors. These results disprove the common belief that MFS structures serve as a good model system for ferroelectric polarization switching in thin-film transistors. cop. 2015 AIP Publishing LLC.

Ferroelectric polarization switching of poly(vinylidene difluoride-trifluoroethylene) is investigated in different thin-film device structures, ranging from simple capacitors to dual-gate thin-film transistors (TFT). Indium gallium zinc oxide, a high mobility amorphous oxide material, is used as semiconductor. We find that the ferroelectric can be polarized in both directions in the metal-ferroelectric-semiconductor (MFS) structure and in the dual-gate TFT under certain biasing conditions, but not in the single-gate thin-film transistors. These results disprove the common belief that MFS structures serve as a good model system for ferroelectric polarization switching in thin-film transistors. cop. 2015 AIP Publishing LLC.

We present the performance of a novel InGaAs/InP single-photon avalanche diode (SPAD) with high detection efficiency and low noise thanks to the improvement of Zinc diffusion conditions and the optimization of the vertical structure. The 25-μm active-area diameter detector, operated in gated-mode with ON time of tens of nanoseconds, shows very low dark count rate (few kilo-counts per second at 225 K and 5 V of excess bias), 30% photon detection efficiency at 1550 nm, low afterpulsing, and a timing response with less than 90-ps full-width at half maximum and very fast exponential tail (time constant ~ 60 ps). Therefore, this InGaAs/InP SPAD is among the best ones ever reported in the literature.

We report in detail on the luminescence imaging setup developed within the last years in our laboratory. In this setup, the luminescence emission of silicon solar cells or silicon wafers is analyzed quantitatively. Charge carriers are excited electrically (electroluminescence) using a power supply for carrier injection or optically (photoluminescence) using a laser as illumination source. The luminescence emission arising from the radiative recombination of the stimulated charge carriers is measured spatially resolved using a camera. We give details of the various components including cameras, optical filters for electro- and photo-luminescence, the semiconductor laser and the four-quadrant power supply. We compare a silicon charged-coupled device (CCD) camera with a back-illuminated silicon CCD camera comprising an electron multiplier gain and a complementary metal oxide semiconductor indium gallium arsenide camera. For the detection of the luminescence emission of silicon we analyze the dominant noise sources along with the signal-to-noise ratio of all three cameras at different operation conditions. © 2011 American Institute of Physics.

In the present work, we report the temperature dependent carrier transport properties of InxGa1-xN thin films in the entire composition range grown by modified activated reactive evaporation. The carrier transport in these degenerate semiconductors is controlled by impurity band conduction. A transition from metallic to semiconducting type resistivity was observed for indium rich films. The semiconducting behavior originates from electron-electron interaction and weak localization, whereas higher temperature scattering contributes to the metallic type resistivity. A transition of resistivity behavior from the quantum phenomena to the classical Arrhenius approach was observed for x 0.12 film. � 2011 American Institute of Physics.

Nanowires show great promise for use in next generation (bio-)chemical sensing devices because of their high surface to volume ratio enabling efficient modulation of their current by charges or dipoles present at the surface. Here, we present a gas sensing device based on vertical InAs nanowire arrays grown without metal catalyst particles. The nanowires are contacted ohmically in their as-grown locations using an air bridge construction, leaving the nanowire surface free for gas adsorption. Noise measurements were performed to determine the measurement resolution for gas detection. The bare devices show sensitivity to NO\2 concentrations well below 75 ppb at room temperature. We furthermore find that these nanowires can be functionalized with metalloporphyrins resulting in sensitivity to both NO\2 and NO concentrations below 75 ppb.

We reported the experimental demonstration of deep-submicrometer inversion-mode In0.75Ga0.25As MOSFETs with ALD high-k AI2O3 as gate dielectric. In this letter, n-channel MOSFETs with 100-200-nm-long gates have been fabricated. At a supply voltage of 0.8 V, the fabricated devices with 200-130-nm-long gates exhibit drain currents of 232-440 A/m and transconductances of 538-705 S/m. The 100-nm device has a drain current of 801 A/m and a transconductance of 940 Sm. However, the device cannot be pinched off due to severe short-channel effect. Important scaling metrics, such as on/off current ratio, subthreshold swing, and drain-induced barrier lowering, are presented, and their relations to the short-channel effect are discussed.

Sensitive biosensors for detection of triglyceride concentration are important. In this paper we report on two types of silicon based triglyceride sensors: an electrolyte-insulator-semiconductor capacitor (EISCAP) which is a potentiometric device and a polysilicon microcantilever. The detection principle for both sensors is based on the enzymatic hydrolysis of triglyceride though the sensing mechanisms are different: electronic for the EISCAP and mechanical for the microcantilever. The characteristics and performances of the two sensors are critically compared. The EISCAP sensor necessitates the presence of a buffer for stable measurements which limits the sensitivity of the sensor at low concentrations of the bioanalyte to 1 mM. The cantilever sensor works without a buffer which improves the lower level of sensitivity to 10 ?m. Both sensors are found to give reproducible and reliable results. � 2008 Elsevier B.V. All rights reserved.

In this study, a novel voltage-mode full-wave rectifier with high-input impedance using a dual-X second-generation current conveyor and three enhancement-type n-channel metal-oxide semiconductor field-effect transistors (MOSFETs) is introduced. The proposed circuit does not employ any passive elements, and is simulated using SPICE program with level 49, 0.25 mu m TSMC CMOS technology parameters to confirm the theory and exhibit the performance of the circuit.

A one dimensional (1D) transfer matrix calculation of current transport in semiconductor nanowires with built-in barriers is described within the effective mass approximation by taking into account (i) the quantum confinement in the radial direction and (ii) the Fermi level position with respect to the 1D sub-band(s), both of which can be determined analytically. We calculate the current-voltage (I-V) characteristic for an InAs nanowire, which has a radius of 200 Å and two 50 Å InP, built-in barriers, which define a 150 Å long InAs quantum disk and find that a peak in the current occurs at an applied voltage of 72 mV, corresponding to resonant tunneling of carriers through the double barriers. This is in good agreement with the I-V curve measured in a similar nanowire at a temperature of 4.2 K, where resonant tunneling occurs at 80 mV. It is deduced that the Fermi level is ≈26 meV above the conduction band edge at the surface of the specific InAs nanowire, which is ten times lower than the Fermi level pinning at inverted InAs thin film surfaces. We discuss the importance of the strain and surface depletion. © 2008 American Institute of Physics. 104

In this Letter, the first spin noise spectroscopy measurements in semiconductor systems of reduced effective dimensionality are reported. The nondemolition measurement technique gives access to the otherwise concealed intrinsic, low temperature electron spin relaxation time of n-doped GaAs (110) quantum wells and to the corresponding low temperature anisotropic spin relaxation. The Brownian motion of the electrons within the spin noise probe laser spot becomes manifest in a modification of the spin noise line width. Thereby, the spatially resolved observation of the stochastic spin polarization uniquely allows to study electron dynamics at equilibrium conditions with a vanishing total momentum of the electron system. © 2008 The American Physical Society.

We have followed by reflection high-energy electron diffraction the nucleation of InAs quantum dots on GaAs(001), grown by molecular-beam epitaxy with growth interruptions. Surface mass transport gives rise, at the critical InAs thickness, to a huge nucleation of three-dimensional islands within 0.2 monolayers (ML). Such surface mass diffusion has been evidenced by observing the transition of the reflection high-energy electron diffraction pattern from two- to three-dimensional during the growth interruption after the deposition of 1.59 ML of InAs. It is suggested that the process is driven by the As2 adsorption-desorption process and by the lowering of the In binding energy due to compressive strain. The last condition is met first in the region surrounding dots at step edges where nucleation predominantly occurs.

Carrier spin polarization in In0.13Ga0.87 As under high electric fields has been investigated. The spin polarization was created by optical spin orientation techniques and the inverse spin-Hall effect was employed to measure the spin polarization. For moderate electric fields, the spin polarization was constant, whereas the significant change in the spin polarization was found in the high electric field range. The spin-density rate equation, together with carrier transport analysis, clarifies that the observed change is attributed to the voltage-induced Auger process which modifies the carrier number in InGaAs. © 2011 American Institute of Physics. 98 24 Cited By :4

We report on single dot microphotoluminescence (μPL) emission at low temperature and low power from InAs dots grown by molecular beam epitaxy in nanoscale holes of a SiO2 mask deposited on GaAs(001). By comparing atomic force microscopy measurements with μPL data, we show that the dot sizes inside the nanoholes are smaller than those of the dots nucleated on the extended GaAs surface. PL of dots spans a wide energy range depending on their size and on the thickness and composition of the InGaAs capping layer. Time-resolved PL experiments demonstrate a negligible loss of radiative recombination efficiency, proving highly effective in the site-controlled dot nucleation.

A controlled method of manipulation of nanowires was found using the tip of an Atomic Force Microscope (AFM). Manipulation is done in the ‘Retrace Lift’ mode, where feedback is turned off for the reverse scan and the tip follows a nominal path. The effective manipulation force during the reverse scan can be changed by varying an offset in the height of the tip over the surface. Using this method, we have studied InAs nanowires on different substrates. We have also investigated interactions between wires and with gold features patterned onto the substrates.

Electromigration and lateral self-diffusion in indium and cobalt thin films were studied using a non-destructive neutron activation tracer scanning technique. The temperature and current density dependences of the electromigration effective charge number Z ∗ were studied in these systems and the results obtained were compared with bulk data. The mechanism of mass transport in the case of the thin film systems studied was due mainly to extended defects such as grain boundaries or surface diffusion. On comparison it is concluded that the established theories developed for explaining bulk mass transport data are not applicable in total in the case of thin films because of basic differences in the mechanism of mass transport.

Neutron activation and tracer scanning technique is employed to estimate the electromigration shift in indium thin films. The electromigration effective charge number Z* is determined as a function of current density at 399 K and it was noticed that 1.40?10 4 A/cm 2 is the threshold current density at this temperature. The variation of Z* with temperature is studied in the temperature range 352-418 K. The value of Z* is negative in the entire temperature range studied. The magnitude of Z* decreases initially, goes to a minimum at 384 K and increases rapidly above this temperature. Autoradiographs of some of the samples are also given which show the electromigration shift very clearly. The initial decrease in the magnitude of Z* is due to the increase of lattice scattering of electrons and the increase close to the melting point is attributed to the grain boundary melting of the material.

Date of Conference: 6-11 May 2007 The electro-optic coefficients of self-organized InAs quantum dot layers in molecular beam epitaxy grown laser structures in reverse bias have been investigated. Enhanced electrooptic coefficients compared to bulk GaAs were observed. © 2003 Optical Society of America.

We have analysed by atomic force microscopy the InAs on GaAs(001) system prepared by molecular beam epitaxy. Subsequent stages of the heteroepitaxial growth have been investigated starting from the initial formation of the strained two-dimensional wetting layer up to the growth of three-dimensional self-assembled quantum dots. In particular, we report on the structural characterization near the critical thickness and discuss the role of different features that influence the morphology of InAs quantum dots.