Electrical properties of thermally evaporated doped and undoped films of CdSe

Electrical characteristics of Ag-doped and undoped films of CdSe have been reported. The activation energies at lower and elevated temperatures have been found to be 0.22 and 0.6eV, respectively. The Sn/CdSe junction exhibits Schottky barrier characteristics with diode ideality factor deviating from unity. Barrier height obtained from C-V plot and J- V plot are 0.8 and 0.72eV, respectively. The junction has been endowed with high series resistance

Effect of substrate temperature on structural properties of thermally evaporated ZnSe thin films

The ZnSe, a wide band gap semiconductor has high potential for application in optoelectronic applications. The structural parameters of a thin film semiconductor largely depend on the preparation method and condition. Transparent ZnSe thin films of thicknesses from 200

Study of Au, Ni-(n)ZnSe thin film Schottky barrier junctions

Schottky barrier junctions of Al-doped n-type Zinc selenide (ZnSe) thin films of doping concentrations up to 9.7×1014cm−3 have been fabricated with Au and Ni electrodes on glass substrates by sequential thermal evaporation. All of the junctions of different doping concentrations exhibited rectifying current-voltage characteristics with a non-saturating reverse current. From the current-voltage characteristics, the different junction parameters such as ideality factor, saturation current density, series resistance, etc., were measured. Both types of junctions were found to possess a high ideality factor and a high series resistance. The barrier heights of the junctions were measured from Richardson plots and found to be around 0.8 eV. The structures were found to exhibit a poor photovoltaic effect with a fill factor not greater than 0.4. The diode quality as well as the photovoltaic performance of the diodes were improved following a short heat treatment in vacuum

Structure and dielectric properties of potassium niobate nano glass-ceramics

Glasses in the composition of 25K(2)O-25Nb(2)O(5)-50SiO(2) (mol %) have been prepared by melt quenching technique and isothermally heat-treated at 800 A degrees C for different duration (0-200 h). The formed nanocrystalline KNbO(3) phase, crystallite size and morphology are examined by X-ray diffraction, Fourier transform infrared reflection spectroscopy, field emission scanning and transmission electron microscopes. The frequency and temperature dependent dielectric constant and loss tangent are measured in the frequency and temperature ranges 0.1-1000 kHz and 200-500 A degrees C respectively. The dielectric constant and loss tangent are found to decrease with increasing frequency and increase with increasing temperature. The dielectric constant and loss tangent versus temperature curve at different frequency revealed the phase transition of KNbO(3) from paraelectric cubic to ferroelectric tetragonal around 425 and 397 A degrees C (Curie temperature) for nano glass-ceramics obtained after 1 and 200 h heat-treatment respectively

Optical and dielectric properties of isothermally crystallized nano-KNbO(3) in Er(3+)-doped K(2)O-Nb(2)O(5)-SiO(2) glasses

Precursor glass of composition 25K(2)O-25Nb(2)O(5)-50SiO(2) (mol%) doped with Er(2)O(3) (0.5wt% in excess) was isothermally crystallized at 800 degrees C for 0-100h to obtain transparent KNbO(3) nanostructured glass-ceramics. XRD, FESEM, TEM, FTIRRS, dielectric constant, refractive index, absorption and fluorescence measurements were carried out to analyze the morphology, dielectric, structure and optical properties of the glass-ceramics. The crystallite size of KNbO(3) estimated from XRD and TEM is found to vary in the range 7-23 nm. A steep rise in the dielectric constant of glass-ceramics with heat-treatment time reveals the formation of ferroelectric nanocrystalline KNbO(3) phase. The measured visible photoluminescence spectra have exhibited green emission transitions of (2)H(11/2). (4)S(3/2) -> (4)I(15/2) upon ;excitation at 377 nm ((4)[(15/2) -> (4)G(11/2)) absorption band of Er(3+) ions. The near infrared (NIR) emission transition (4)[(13/2) -> 4[(15/2) is detected around 1550 nm on excitation at 980 mn ((4)[(15/2) -> 4 [(11/2)) of absorption bands of Er(3+) ions. It is observed that photoluminescent intensity at 526 nm ((2)H(11/2) -> (4)I(15/2)), 550nm (4S(3/2) -> (4)I(15/2)) and 1550nm ((4)I(13/2) -> (4)I(15/2)) initially decrease and then gradually increase with increase in heat-treatment time.'rhe measured lifetime (tau(f)) of the (4)I(13/2) -> (4)I(15/2) transition also possesses a similar trend. The measured absorption and fluorescence spectra reveal that the Er(3+) ions gradually enter into the KNbO(3) nanocrystals. (C) 2009 Elsevier B.V. All rights reserved

Structure, dielectric and optical properties of transparent Nd(3+):KNbO(3) nanocrystalline glass-ceramics

Here, glass in the composition of 25K2O–25Nb2O5–50SiO2 (mol%) doped with Nd2O3 (0.5 wt.% in excess)was isothermally crystallized at 800 C for 1–100 h. Their structures, dielectric and optical properties were analyzed with the progress of nanocrystallization of Nd3+: KNbO3 by XRD, FESEM, TEM, FTIRRS, DC, optical absorption and fluorescence measurements. Crystallization of KNbO3 is confirmed from XRD and the appearance of 749 cm-1 band in the FTIRRS spectra. The crystallite size estimated from XRD and TEM is found to vary in the range 7–11 nm. The formation of ferroelectric nano-crystalline KNbO3 phase is also attributed by a steep rise in the dielectric constant (e) of glass–ceramics with heat-treatment time. The measured photoluminescence spectra have exhibited emission transitions of 4F3/2?4IJ (J = 9/2, 11/2 and 13/2) from Nd3+ ions upon excitation at 817 nm. It is observed that the photoluminescent intensity and excited state lifetime of Nd3+ ions initially decrease and then gradually increase with increase in heat-treatment time. The absorption spectra and fluorescence measurements disclose that the Nd3+ ions gradually enter into the KNbO3 nanocrystals