85 research outputs found
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
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