A method has been developed to synthesize metal and metal oxide nanostructures in high yields on the
surface of SiO2/Si substrate. In this method, starting materials in a covered alumina crucible are thermally
evaporated under a high vacuum or a low pressure of ambient air. Spherical gold nanoparticles with a
size of 15nmand nanowires with a diameter of 70nmwere synthesized. SnO2 rough microwires, smooth
nanowires, and nanoknives were synthesized by using Sn granules, SnO powder, and SnO2 powder as
source materials, respectively. The microwires showed a quadrangular cross section and a length of
several microns, while the nanowires showed a circular cross section and approximately the same length.
The effects of source temperature and deposition time on nanostructure growth were studied. X-ray
diffraction patterns suggested that the as-synthesized products consisted of crystalline nanostructure.
Nanocomposite gas sensors on the base of noble metal and metal oxide were fabricated. These SnO2
nanowire gas sensors showed a reversible response to dilute NO2 gas at operating temperatures ranging
between room temperature and 300 ◦C even at high concentrations. The results demonstrated that gold
doping improved the sensor response.

Electrodes with micro-gaps are fabricated by using dc-sputtering and FIB techniques. SnO2 nanowires
are deposited on the micro-gap (1–30 m) by suspension dropping method to fabricate a micro-gas
sensor. The sensing ability of various SnO2 micro-gap sensors is measured. A comparison between sensors
reveals that the short-gap electrode has numerous advantages in terms of reliability, high sensitivity and
detection of low concentrations of NO2, while the large-gap electrode is relatively sensitive for high
concentrations. Conductance measurements are carried out at different surface temperatures and NO2
concentrations in order to investigate the effects that the gap size has on the overall sensor conductance.
The results suggest that the interface between the electrode and sensitive layer has a very important role
for the sensing mechanism of tin dioxide gas sensors.

SnO2 microwires, nanowires and rice-shaped nanoparticles were synthesized by a thermal evaporation
method. The diameters of microwire and nanowire were 2mand 50–100 nm, respectively, with approximately
the same length (∼20m). The size of nanoparticles was about 100 nm. It was confirmed that
the as-synthesized products have SnO2 crystalline rutile structure. The sensing ability of SnO2 particle
and wire-like structure configured as gas sensors was measured. A comparison between the particle and
wire-like structure sensors revealed that the latter have numerous advantages in terms of reliability and
high sensitivity. Although its high surface-to-volume ratio, the nanoparticle sensor exhibited the lowest
sensitivity. The high surface-to-volume ratio and low density of grain boundaries is the best way to
improve the sensitivity of SnO2 gas sensors, as in case of nanowire sensor which exhibited a dramatic
improvement in sensitivity to NO2 gas.

Different compositions of Bi5GexSe95
x (x ¼ 30, 35, 40 and 45 at %) thin films were deposited onto
cleaned glass substrates by thermal evaporation method. The structural characterization revealed that,
the as-prepared films of x ¼ 30, 35 and 40 at. % are in amorphous state but there are few tiny crystalline
peaks of relatively low intensity for the film with x ¼ 45 at. %. The chemical composition of the asprepared
Bi5GexSe65
x films has been checked using energy dispersive X-ray spectroscopy (EDX). The
optical properties for the as-deposited Bi5GexSe65
x thin films have been studied. The additions of Ge
content were found to affect the optical constants (refractive index, n and the extinction coefficient, k).
Tauc’s relation for the allowed indirect transition is successfully describing the mechanism of the optical
absorption. It was found that, the optical energy gap (Eg) decreases with the increase in Ge content. These
obtained results were discussed in terms of the chemical bond approach proposed by Bicermo and
Ovshinsky. The composition dependence of the refractive index was discussed in terms of the single
oscillator model.

The effectofannealinginnitrogenatmosphereonstructuralandelectricalpropertiesofseleniumrich
CdSe (SR-CdSe)thinfilmsdepositedbythermalevaporationontoglasssubstrateswerestudied.X-ray
diffraction(XRD)patternsshowedthattheas-preparedfilmswereamorphous,whereastheannealed
filmswerepolycrystalline.AnalyzingXRDpatternsrevealsthecoexistenceofbothSeandCdSe
crystallinephaseswhichexhibitsahexagonalstructure.Themicrostructureparameters(crystallite
size, microstrainanddislocationdensity)werecalculatedforannealedfilms.
Temperaturedependence(300–500K)ofd.c.conductivitywasstudiedforas-preparedand
annealedthinfilms.Theexperimentalresultsindicatethattheelectricalconductiontakingplace
throughthermallyactivatedprocess.Athighertemperatures,electricalconductionforas-preparedfilm
is takingplaceintheextendedstateswhilelocalizedstatesconductioninthebandtailsismostlikelyto
take placeforannealedfilms.Regardingthelowertemperaturerange,conductionbyhoppinginthe
localizedstatesneartheFermilevelisfoundtobedominant.Thus,conductivitydatainthisrangewas
analyzedusingMott’svariablerangehoppingconduction,whereMott’sparameterswerecalculatedfor
SR-CdSe thinfilms.

Structural and optical properties of selenium-rich CdSe (SR-CdSe) thin films prepared by thermal evaporation
are studied as a function of annealing temperature. X-ray diffraction (XRD) patterns show that
the as-prepared films were amorphous, whereas the annealed films are polycrystalline. Analyzing XRD
patterns of the annealed films reveal the coexistence of both (hexagonal) Se and (hexagonal) CdSe crystalline
phases. Surface roughness of SR-CdSe films is measured using atomic force microscope (AFM).
Analyses of the absorption spectra in the wavelength range (200–2500 nm) of SR-CdSe thin films indicates
the existence of direct and indirect optical transition mechanisms. The optical band gap (Eg) of
as-prepared film is 1.92 and 2.14 eV for the indirect allowed and direct allowed transitions respectively.
After annealing, the absorption coefficient and optical band gap were found to decrease, while the values
of refractive index (n) and the extinction coefficient (kex) increase. The dispersion of the refractive index is
described using the Wimple–Di Domenico (WDD) single oscillator model and the dispersion parameters
are calculated as a function of annealing temperature. Besides, the high frequency dielectric constant
(ε∞) and the ratios of the free carrier concentration to its effective mass (N/m*) are studied as a function
of annealing temperature. The results are discussed and correlated in terms of amorphous-crystalline
transformations.

Structural and optical properties of selenium-rich CdSe (SR-CdSe) thin films prepared by thermal evaporation
are studied as a function of annealing temperature. X-ray diffraction (XRD) patterns show that
the as-prepared films were amorphous, whereas the annealed films are polycrystalline. Analyzing XRD
patterns of the annealed films reveal the coexistence of both (hexagonal) Se and (hexagonal) CdSe crystalline
phases. Surface roughness of SR-CdSe films is measured using atomic force microscope (AFM).
Analyses of the absorption spectra in the wavelength range (200–2500 nm) of SR-CdSe thin films indicates
the existence of direct and indirect optical transition mechanisms. The optical band gap (Eg) of
as-prepared film is 1.92 and 2.14 eV for the indirect allowed and direct allowed transitions respectively.
After annealing, the absorption coefficient and optical band gap were found to decrease, while the values
of refractive index (n) and the extinction coefficient (kex) increase. The dispersion of the refractive index is
described using the Wimple–Di Domenico (WDD) single oscillator model and the dispersion parameters
are calculated as a function of annealing temperature. Besides, the high frequency dielectric constant
(ε∞) and the ratios of the free carrier concentration to its effective mass (N/m*) are studied as a function
of annealing temperature. The results are discussed and correlated in terms of amorphous-crystalline
transformations.

Structural and optical properties of selenium-rich CdSe (SR-CdSe) thin films prepared by thermal evaporation
are studied as a function of annealing temperature. X-ray diffraction (XRD) patterns show that
the as-prepared films were amorphous, whereas the annealed films are polycrystalline. Analyzing XRD
patterns of the annealed films reveal the coexistence of both (hexagonal) Se and (hexagonal) CdSe crystalline
phases. Surface roughness of SR-CdSe films is measured using atomic force microscope (AFM).
Analyses of the absorption spectra in the wavelength range (200–2500 nm) of SR-CdSe thin films indicates
the existence of direct and indirect optical transition mechanisms. The optical band gap (Eg) of
as-prepared film is 1.92 and 2.14 eV for the indirect allowed and direct allowed transitions respectively.
After annealing, the absorption coefficient and optical band gap were found to decrease, while the values
of refractive index (n) and the extinction coefficient (kex) increase. The dispersion of the refractive index is
described using the Wimple–Di Domenico (WDD) single oscillator model and the dispersion parameters
are calculated as a function of annealing temperature. Besides, the high frequency dielectric constant
(ε∞) and the ratios of the free carrier concentration to its effective mass (N/m*) are studied as a function
of annealing temperature. The results are discussed and correlated in terms of amorphous-crystalline
transformations.

Bi5GexSe95
x (30, 35, 40 and 45 at.%) thin films of thickness 200 nm were prepared on glass substrates by
the thermal evaporation technique. The influence of composition and annealing temperature, on the
structural and electrical properties of Bi5GexSe95
x films was investigated systematically using X-ray
diffraction (XRD), energy dispersive X-ray analysis (EDX). The XRD patterns showed that the as-prepared
films were amorphous in nature with few tiny crystalline peaks of relatively low intensity for 30 and
45 at.% and the Bi5Ge40Se55 annealed film was polycrystalline. The chemical composition of the Bi5Ge30Se65
film has been checked using energy dispersive X-ray spectroscopy (EDX). The electrical
conductivity was measured in the temperature range 300e430 K for the studied compositions. The effect
of composition on the activation energy (DE) and the density of localized states at the Fermi level N(EF)
were studied, moreover the electrical conductivity was found to increase with increasing the annealing
temperature and the activation energy was found to decrease with increasing the annealing temperature.
The results were discussed on the basis of amorphous-crystalline transformations.

Theoretical calculations are described to investigate the behavior of solid explosive when heated by
continuous and pulsed laser. A one-dimensional model is proposed and the numerical solutions have
been obtained for the time-dependent nonlinear heat equation with the appropriate initial and boundary
conditions. Relationships between various ignition parameters are analyzed and possible ignition
mechanisms are discussed. Theoretical calculations are applied to the primary solid explosive b lead
azide. It has been argued that the initiation of b lead azide with low energy laser is thermal in origin.