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In this manuscript, the structural, opto-electronic, and thermodynamic properties of Zn[Al.sub.2][Se.sub.4] chalcogenide compounds were studied in detail using the full potential linearized augmented plane wave method. The exchange and correlation potentials used in density functional theory were calculated using local density approximation, the generalized gradient approximation (GGA) method, and the modified Becke-Johnson (mBJ) potential using Wien2k code. The obtained results were compared with each other as well as with available experimental data. At ambient conditions, Zn[Al.sub.2][Se.sub.4] is a direct wide bandgap ([GAMMA]-[GAMMA]) semiconductor with a bandgap of 2.1 and 3.3 eV with GGA and mBJ potentials, respectively. Density of states (DOS; total DOS and Partial Density Of States (PDOS)) and electron density contour plots were in similar accordance with bandgap, showing semiconductive behavior and covalent bonding nature. The optical properties like the real and imaginary parts of the dielectric constant, the energy loss function L([omega]), and the conductivity [sigma]([omega]) were calculated. Optical aspects show interaction among phonon and electron in terms of long-range and short-range forces. The studied compound is very useful for various linear-nonlinear optical devices, so this compound is very valuable for several linear-nonlinear optical devices. So this manuscript represents a comprehensive approach for calculating the complete set of useful properties of the Zn[Al.sub.2][Se.sub.4] compound, which can provide support for understanding various device phenomena such as electrochemical sensing, photovoltaics, and nonvolatile electronic memories. Keywords: chalcogenide compounds, first-principles study, opto-electronic property, modified Becke-Johnson (mBJ) potential, 1. Introduction The majority of the growing problems can be handled by using leading renewable energy resources like solar energy. Nowadays, considerable ongoing research is dedicated to ternary semiconductors [A.sup.II][B.sub.2.sup.III][C.sub.4.sup.VI] [...]

We investigated the electrical properties of the In-Ga-Zn-O (IGZO) film under light illumination. We measured the photoconductivity of a-IGZO thin film under light illumination with various intensities. We extracted the photoexcitation activation energy and dark relaxation activation energy through extended stretched exponential analysis. Dark relaxation characteristics, which are related to the recombination process, show longer time constant, τ, larger effective activation energy [E.sub.ac], and lower stretching exponent, β, with wider activation energy bandwidth, [Δ.sub.ac], than those corresponding to those of photoexcitation. These indicate that recombination takes place more slowly and through more deeply bound activation processes with the broader distribution of activation energies than those corresponding to photogeneration process. The wider distribution for the dark relaxation energy for the higher light intensity suggests that the metastable state distribution is related to the distribution of the oxygen vacancy state, [V.sub.o]. We also concluded that the usage of the right value of the attempt-to-escape frequency is important to estimate the exact value of [E.sub.ac]. PACS Nos.: 73.50.Pz, 73.50.-h, 73.61.-r. Nous etudions les proprietes electriques de films de In-Ga-Zn-O (IGZO) sous eclairage lumineux. Nous mesurons la photoconductivite de films minces de a-IGZO sous illumination d'intensite variable. L'analyse etendue par exponentielle etiree nous permet d'extraire l'energie d'excitation d'activation et l'energie de relaxation d'activation en obscurite. Les caracteristiques de relaxation en obscurite, qui sont reliees au mecanisme de recombinaison, montrent une plus grande constante de temps, τ, de plus grandes energies d'activation efficaces, [E.sub.ac], et de plus faibles exposants d'etirement, β, avec une plus large largeur de bande d'energie d'activation, [Δ.sub.ac], que celles correspondant a la photo-excitation. Elles indiquent que la recombinaison se produit plus lentement et via un processus d'activation plus profondement lies avec de plus larges distributions d'energies d'activation que celles correspondant au procede de photo-generation. Ajoutons que la plus large distribution de l'energie de relaxation en obscurite pour des intensites lumineuses plus elevees, suggere que la distribution d'etats metastables est reliee a la distribution de l'etat [V.sub.o] lacunaire d'oxygene. Nous concluons aussi que l'utilisation de la bonne valeur de la frequence des essais-de-fuite est importante pour calculer la bonne valeur de [E.sub.ac]. [Traduit par la Redaction], 1. Introduction Nowadays, amorphous In-Ga-Zn-O thin film transistors (a-IGZO TFTs) are getting a lot of attention from many researchers [1-4]. Compared to other devices, such as a hydrogenated amorphous silicon [...]

In this work, rutile-phase Ti[O.sub.2] particles (r-Ti[O.sub.2], about 360 nm in size) are embedded within a silicon oxide matrix using different concentration ratios of r-Ti[O.sub.2] with respect to Si[O.sub.2]:[H.sub.2]O, so that suspensions of mixed Ti[O.sub.2]:Si[O.sub.2] oxides were obtained and analyzed. These Ti[O.sub.2]:Si[O.sub.2] suspensions were deposited on previously-cleaned crystalline silicon and quartz substrates so that thin films of Ti[O.sub.2]:Si[O.sub.2] were obtained. All films were then exposed to relatively high-temperature thermal treatments in nitrogen and different characterization techniques were used to determine their physical and electrical properties before and after ultraviolet (UV) irradiation. Before high thermal treatment, X-ray diffraction patterns show that the main diffraction peaks for the obtained Ti[O.sub.2]:Si[O.sub.2] films correspond to the crystalline phase of rutile-Ti[O.sub.2]. Infrared analyses before and after thermal treatment show significant changes in the chemical bonding of the final films relative to the temperatures used during annealing. Also, UV-visible spectra provide a constant optical band gap for the films, independent of different Ti[O.sub.2] concentrations as expected. On the other hand, atomic-force microscopy measurements before and after UV irradiation show an appreciable difference in the grain size and surface morphology of the resulting Ti[O.sub.2]:Si[O.sub.2] oxides annealed at 1000 °C. Finally, photoelectrical I-V properties were obtained for all Ti[O.sub.2]:Si[O.sub.2] films by depositing ultrathin titanium stripes on top of the photoactive material and then, measuring the total current flowing through the metal electrode before and after UV irradiation. From these last measurements, a detectable increase in the I-V slope (lower resistance of the titanium stripe) is found for all samples during UV exposure, thus making this device to act as a simple photoresistor based on r-Ti[O.sub.2] particles. PACS Nos.: 78.67.Bf, 73.50.Pz, 61.80.Ba. Des particules de Ti[O.sub.2] en phase rutile (r-Ti[O.sub.2], environ 360 nm) sont ici implantees dans une matrice d'oxyde de silicium, utilisant differentes concentration de r-Ti[O.sub.2] relativement au Si[O.sub.2] : [H.sub.2]O, de facon a pouvoir obtenir et analyser differentes suspensions de Ti[O.sub.2] : Si[O.sub.2]. Ces suspensions sont deposees en films minces de Ti[O.sub.2] : Si[O.sub.2] sur des substrats de silicium cristallin et de quartz prealablement nettoyes. Tous les films sont recuits a relativement haute temperature dans une atmosphere d'azote et nous utilisons differentes techniques pour caracteriser leurs proprietes physiques et electriques avant et apres leur irradiation aux ultraviolet (UV). Avant le traitement thermique, les patrons de diffraction X indiquent que les principaux pics de diffraction des films de Ti[O.sub.2] : Si[O.sub.2] correspondent a la phase cristalline de r-Ti[O.sub.2]. L'analyse infrarouge avant et apres le traitement thermique montre des changements significatifs dans le lien chimique des films finaux selon les temperatures utilisees pour le recuit. De plus, la spectroscopie UV-visible indique un gap optique constant pour les films, independamment de la concentration en Ti[O.sub.2], tel qu'attendu. D'un autre cote, la microscopie a force atomique avant et apres l'irradiation UV montre une difference appreciable de la grosseur du grain et de la morphologie de surface des oxydes resultants Ti[O.sub.2] : Si[O.sub.2] soumis a un recuit a 1000°C. Finalement, nous determinons les proprietes photoelectriques I-V de tous les films de Ti[O.sub.2] : Si[O.sub.2], en deposant sur le materiau photo-actif une ultra-mince languette de titane et en mesurant le courant total dans cette electrode metallique avant et apres l'irradiation aux UV. De ces mesures, nous trouvons une augmentation detectable dans la pente I-V (plus basse resistance de la languette de Ti) pour tous les echantillons durant l'exposition aux UV, determinant ainsi que ce dispositif est une simple photoresistance basee sur les particules de r-Ti[O.sub.2]. [Traduit par la Redaction], 1. Introduction Since the 1920s, titanium dioxide (Ti[O.sub.2]) has been produced commercially for applications in paints, sunscreens, toothpaste, pigments, etc., but it was not until 1972 that Fujishima and Honda [...]

The crystallization of hydrogenated amorphous silicon films with femtosecond laser pulses is one of the promising ways to produce nanocrystalline silicon for photovoltaics. The structure of laser treated films and their hydrogen content are the most important factors for determining the photoelectric properties of materials. In this work we investigated the effect of femtosecond laser irradiation of a-Si:H films with different fluences on crystalline volume fraction, hydrogen concentration, and photoelectric properties of this material. Our results point out that hydrogen out-diffusion accompanies the crystallization process. The increase of hydrogen concentration in the initial a-Si:H films structure affects the kinetics of the crystallization process, but does not lead to a substantial increase of hydrogen concentration remaining in the film after the treatment. The deficiency of hydrogen in the films' structure results in degradation of their photoconductivity, thus other strategies of a-Si:H laser crystallization or postprocessing should be found to obtain device-quality films using ultrafast laser processing. PACS Nos.: 71.23.Cq, 73.50.Pz, 79.20.Ds. La cristallisation par impulsion laser femto-seconde de films de silicium amorphe hydrogene est l'un des moyens prometteurs pour produire du silicium nanocristallin pour utilisation photovoltaique. La structure des films traites par laser et leur contenu en hydrogene sont les facteurs les plus importants qui determinent les proprietes photoelectriques du materiau. Nous etudions ici les relations de l'irradiation laser femto-seconde sur des films de a- Si:H, avec differents intensites sur la fraction cristalline en volume, la concentration en hydrogene et les proprietes photoelectriques du materiau. Nos resultats suggerent qu'une perte d'hydrogene par diffusion accompagne le mecanisme de cristallisation. L'augmentation de la concentration initiale d'hydrogene dans les films de a-Si:H affecte la cinetique de la cristallisation, mais ne mene pas a une augmentation significative de la concentration d'H dans le film apres traitement. Le manque d'hydrogene dans les films degrade leurs proprietes photoelectriques. Ainsi, on doit trouver d'autres strategies de cristallisation de a-Si:H par laser ou un post-traitement, afin d'obtenir des films de qualite par irradiation laser ultra-rapide. [Traduit par la Redaction], Introduction In the last few decades, films of nanocrystalline hydrogenated silicon (nc-Si:H) have attracted a lot of attention because of their potential applications in solar cells, thin film transistors, and [...]

The photodetachment of [H.sup.-] ions in a nonuniform electric field has been investigated on the basis of closed orbit theory. Firstly, we give a clear physical description of the detached electron's movement in a nonuniform electric field. Then we put forward an analytical formula for calculating the photodetachment cross section of this system. Our study suggests besides the closed orbit previously reported for the photodetachment of [H.sup.-] in a uniform electric field, some additional closed orbits are produced owing to the effect of the nonuniform electric field. Compared with the photodetachment cross section of [H.sup.-] in a uniform electric field, the oscillation in the cross section of our system becomes much more complicated and the cross section exhibits a multiperiodic oscillatory structure. To show the relation between the oscillation in the photodetachment cross section and the detached electron's classical closed orbits clearly, we make a Fourier transformation for the scaled photodetachment cross section of this system. Each peak in the Fourier transformed cross section corresponds to the contribution of one closed orbit. This study provides a new understanding of the photodetachment of negative ions in the presence of a nonuniform electric field. PACS Nos.: 34.35.+a, 32.80.Gc, 32.80.Qk, 42.50.Hz. Nous etudions le photo-detachement de l'ion [H.sup.-] dans un champ electrique non uniforme, sur la base de la theorie de l'orbite fermee. Nous donnons d'abord une description detaillee du mouvement de l'electron detache dans un champ electrique non uniforme. Ensuite, nous proposons une formule analytique pour la section efficace de photo-detachement de ce systeme. En plus de l'orbite fermee prealablement rapportee pour le photo-detachement de [H.sup.-], notre etude suggere des orbites fermees additionnelles dues a la non uniformite du champ electrique. La comparaison avec la section efficace de photo-detachement de [H.sup.-] en champ electrique uniforme montre que l'oscillation de la section eficace de notre systeme devient beaucoup plus compliquee et cette section eficace presente une structure oscillante multiperiodique. Nous operons la transformation de Fourier de la section eficace de ce systeme ain de montrer clairement la relation entre l'oscillation de la section eficace de photo-detachement et les orbites classiques fermees de l'electron detache. Chaque pic de la transformation correspond a la contribution d'une orbite fermee. Ces resultats jettent une lumiere nouvelle sur le photo-detachement d'ions negatifs en presence d'un champ electrique non uniforme. [Traduit par la Redaction], 1. Introduction The photodetachment of [H.sup.-] in various external fields has been studied by many authors over the past 20 years. Pioneering measurements of the photodetachment cross section of [H.sup.-] [...]

The gamma irradiation technique has been used to alter the dielectric and electro-optical properties of a liquid crystal material. The present paper reports a comparative study of dielectric and electro-optical properties of unirradiated EBHA nematic liquid crystal (NLC) with gamma-irradiated EBHA NLC. The dielectric measurement has been performed with variation in voltage and temperature within the frequency range 100 Hz-10 MHz. Variations in response time for both gamma- irradiated and unirradiated samples have also been measured and are well explained in the present paper. PACS Nos.: 77.84.Nh, 78.20.Ci, 77.22.Gm, 76.80.+y, 78.20.Jq. Nous soumettons un cristal liquide a une irradiation gamma, afin de modifier ses proprietes dielectriques et electrooptiques. Nous comparons ici les proprietes dielectriques et electro-optiques d'un cristal liquide nematique (NLC) EBHA non irradie avec celles d'un NLC EBHA irradie. Les mesures dielectriques sont faites avec variation de voltage et de temperature dans le domaine de 100 Hz a 10 MHz. Nous mesurons et expliquons egalement les variations dans le temps de reponse pour les deux echantillons, irradie et non irradie. [Traduit par la Redaction], 1. Introduction The modification in dielectric and electro-optical properties of liquid crystal (LC) caused by ion beam radiation is a new field of research. Ionizing particles like electrons, photons, and [...]

The systematic trends of electronic structure and optical properties of Ru[O.sub.2] consisting of its four phases have been studied by using norm-conserving pseudopotential within the generalized gradient approximation for the exchange- correlation potential. The total density of states (DOS) and energy band structure investigations revealed that the fluorite phase possesses the broadest conduction bandwidth (0-30 eV) and the pyrite phase possesses the narrowest conduction bandwidth (0-5 eV). Study on partial DOS we found that O 2p electrons of the fluorite phase present a significant shift towards the Fermi level and Ru s and p electrons of the rutile phase contribute little to the orbital energy level formation. For the first time, we found that the norm-conserving pseudopotential failed to obtain the normal DOS and energy band distributions for a rutile Ru atom below about -10 eV, whereas such missing electronic distributions could be obtained successfully using an ultrasoft pseudo potential. Investigations on the optical properties further found that the rutile and Ca[Cl.sub.2]-type phases behave more similarly and the fluorite phase shows the most sensitive response in the whole radiation reaction region. The electron energy loss function revealed that the pyrite phase corresponds to the least relative intensity. PACS Nos: 63.20.dk, 71.20.-b, 78.20.Ci Nous utilisons un pseudo-potentiel a norme conservee dans l'approximation du gradient generalise pour obtenir le potentiel d'echange-correlation, afin d'etudier les tendances systematiques de la structure electronique et des proprietes optiques du Ru[O.sub.2], incluant ses quatre phases. La densite totale d'etats (DOS) et la structure de la bande d'energie revelent que la phase fluorite possede la plus grande largeur de bande de valence (0-30 eV) et que la phase pyrite possede la plus etroite (-20-0 eV). Etudiant les DOS partielles, nous trouvons que les electrons 2p de O dans la phase fluorite montrent un deplacement marque vers le niveau de Fermi, alors que les electrons s et p du Ru dans la phase rutile contribuent peu aux niveaux d'energie orbitaux. Pour la premiere fois, nous trouvons que le pseudo-potentiel a norme conservee echoue a obtenir la DOS normale et les distributions de bande d'energie pour le Ru rutile sous -10 eV, alors que de telles distributions sont obtenues avec succes a partir de pseudo-potentiels ultra mous. Etudiant les proprietes optiques, nous trouvons que les phases rutile et du type Ca[Cl.sub.2] sont plus proches et que la phase fluorite a la reponse la plus sensible sur toute la region de reaction radiative. La fonction de perte d' energie electronique revele que la phase pyrite a la plus faible intensite relative. [Traduit par la Redaction], 1. Introduction The low resistivity and reactivity of Ru[O.sub.2] has made it technologically important as a strip-line conductor in integrated circuits, as a diffusion barrier in contact metallizations, etc. [1, [...]