Stable electrical,morphological and optical properties of titanium dioxide nanoparticles affected by annealing temperature

Different TiO₂ synthesization processes give different properties. Most of researches in material studies only focus on the morphological and optical properties of TiO₂ while lacking in the effort of achieving stable electrical properties of the material. In engineering, stable electrical properties are vital in order to develop a device. Moreover, current technology needs more nanostructure application to enhance the performance of devices. In this paper, TiO₂ nanoparticle was synthesized by sol–gel method using 1:0.1:9 ratios of titanium isopropoxide:acetic acid:ethanol, respectively. This synthesized TiO₂ was able to respond in extremely small and consistent electrical reading (nanoampere). This metal oxide is good enough to be used as a material to develop ultra-high sensitive biosensor. Annealing process on the TiO₂ film was able to improve its’ electrical conductivity. The three layers TiO₂ coating were annealed at 400, 500, 600 and 700 °C and the surface morphologies, structural also electro-optical properties were studied using FESEM, XRD, UV–Vis and Keithley 6485 picoammeter. The XRD pattern shows the presence of stable anatase and rutile structures even at low temperature, whereas FESEM shows that annealing temperature affects the particle size. The optical band gap of TiO₂ thin films decreases from 3.74 to 3.34 eV as the annealing temperature increases. The current-to-voltage characteristics show that the conductivity decreases as the annealing temperature varies from 400to 700 °C. The output measurements indicated an improvement in electrical properties with annealing temperature.

     

Influence of Si co-doping on magnetic, electrical and optical properties of Ga_(1-x)Mn_xN film grown by MOCVD

A detailed study is presented on magnetic, electrical and optical properties of Ga 1-x Mn x N: Si film grown by metal organic chemical vapor deposition (MOCVD) with high-purity SiH 4 as the Si dopant source. The room-temperature field dependence magnetization and zero-field-cooled (ZFC)/field-cooled (FC) measurements indicate that the film remains room-temperature ferromagnetism and it declines slightly after Si co-doping. However, room-temperature Hall measurements indicate that the electrical property of ...     

Synthesis of ScAlN thin films on Si (100) substrates at room temperature

Microsystem Technologies - Scandium aluminum nitride alloy (ScAlN) thin films have been synthesized using reactive sputtering of a scandium aluminum alloy (Sc0.40Al0.60) target on Si (100)...     

Analysis of interaction between chemical agents and porous Si nanostructures using optical sensing properties of infra-red Rugate filters

Porous silicon based optical Rugate filters operating in the infra-red spectral range have been used to study chemical modifications (alkylation and oxidation) of the porous silicon internal specific surface. Influences of the chemical modifications on the filter response and on its sensitivity for solvent detection is described in details. Important quantitative information concerning structure and chemical coating of the filters is obtained. Application of the porous filters for the detection of different solvents filling their nanopores is studied.     

Pinecone-shaped ZnO nanostructures: Growth, optical and gas sensor properties.

Pinecone-shaped ZnO nanostructures have been fabricated on Si substrate by pulsed laser deposition. The scanning electron microscope images showed that pinecone-shaped ZnO nanostructure was 6-fold symmetry and has the rough surface on one end. X-ray diffraction, Raman spectra and X-ray photoelectron spectroscopy indicated that the ZnO nanostructures have high crystal quality and a large amount of surface states. Compared with ZnO nanowires and nanobelts, the oxygen gas sensor based on pinecone-shaped ZnO nanostructures has excellent selectivity, fast response and recover, and lower operating temperature. Meanwhile, the response properties are very stable over several circles.     

Structural, optical and electrical properties of CdO/Cd(OH)2 thin films grown by the SILAR method

Successive Ionic Layer Adsorption and Reaction (SILAR) was used to form Cd(OH)₂ thin films from aqueous cadmium–ammonia complex on glass substrates at room temperature and the thermal annealing effect on thin films was studied. The as-deposited films were annealed at 200, 300 and 400 °C for 1 h in an oxygen atmosphere for conversion from Cd(OH)₂ to CdO and change in the structural, optical and electrical properties of the films and the effect of the light on the electrical properties of the films were investigated. The structural and surface morphological properties of the films were studied using X-ray diffraction (XRD) and scanning electron microscopy (SEM). It was found that Cd(OH)₂ phase is converted into the cubic CdO films by annealing. The band gap energy values of films decreased from 3.59 to 2.13 eV through increasing annealing temperature. It was found that the current increased with increasing light intensity and CdO films were more conductive than the as-deposited films.     

Laser-induced etching parameters impact on optical properties of the silicon nanostructures

Porous silicon (PS) was fabricated by laser-induced etching (LIE) process. The objective of this study is to investigate the selected LIE parameters to control size and shape of nanostructures,which are considered important factors in semiconductor device applications. Photoluminescence output intensity becomes stronger due to the increase in the number of emitted photons on the porous surface. There is a dramatic increase in photoluminescence intensity due to the increase of porosity as a function of laser...     

Effects of temperature and pressure on the structural and optical properties of ZnO films grown by pulsed laser deposition

ZnO thin films were deposited on fused silica via pulsed laser deposition (PLD) at substrate temperatures from 300°C to 800°C and ambient oxygen pressures ranging from 10-2 mTorr to 240 mTorr. X-ray diffraction (XRD) and Raman spectra indicated that wurtzite ZnO was obtained in all cases. The highly c-oriented ZnO films were obtained for oxygen pressures above 11 mTorr. The room-temperature photoluminescence (PL) spectra demonstrated that all the films exhibited strong near-band-edge (NBE) emission, while d...     

Microstructural and electrical properties of 0.65Pb(Mg1/3Nb2/3)O3-0.35PbTiO3 (PMN-PT) epitaxial films grown on Si substrates

Epitaxially grown PMN-PT thin films using the PMN-PT single crystal targets were prepared at 550 °C on appropriate buffer layers of LSCO/CeO₂/YSZ deposited on a Si substrate using pulsed laser deposition. The micro-structural and the electrical properties of the films were investigated as a function of the film thickness. The PMN-PT films with the thickness from 200 to 600 nm exhibited an epitaxial nature with a pure perovskite structure. On the other hand, the films above 700 nm included a pyrochlore phase embedded in the perovskite structure although they exhibited an epitaxial nature. A pyrochlore phase included in the films above 700 nm thickness decreased the dielectric constant and the ferroelectric properties of the PMN-PT films.     

Synthesis and optical properties of iron doped gallium nitride nanostructures by sol gel method

Recently, wide band-gap III-Nirtride (III-N) materials and its alloys have attracted much research due to its unique properties and diverse field of applications. In the present study, GaN with various concentration of iron (Fe) in the range 0–5 at% nanostructures were prepared by facile solution process using (Ga(NO₃)₃·9H₂O), iron (III) chloride hexahydrate (FeCl₃·6H₂O) at mild temperature for the first time. The microstructure was analyzed by means of X-ray diffraction and atomic force microscopy. The detailed studies demonstrate that the as-synthesized nanoparticles are well crystallined GaN with a hexagonal wurtzite structure and having the average size of 31 nm in diameter. The optical properties of as the prepared GaN are investigated for Fe doping concentrations ranging from 0.1 to 5 at%. The optical band gap value increases with increasing Fe concentration. These results suggest that the Fe doped-GaN is a promising candidate for optoelectronics and spintronics devices.     

Computational study of structural,optoelectronic and nonlinear optical properties of dynamic solid-state chalcone derivatives

In the present study, we use the state of art density functional theory (DFT) techniques to calculate the structural, optoelectronic and nonlinear optical (NLO) properties for two novel chalcone derivatives. The geometrical structures of chalcone derivatives compound 1 and 2 are optimized using periodic boundary conditions (PBC) in solid-state phase as well as isolated single molecular geometry in the gas phase. The reasonable agreement is found among experimental, solid-state and gas phase single molecular geometries, which provide us, further confidence to explore the potential of above-entitled derivatives as good functional materials for electro-optical applications. For instance, the frequency dependent real parts of dielectric functions are calculated for compound 1 and 2. The maximum value of real part of the dielectric function for compound 1 and 2 at 0 eV are computed as 4.35 and 6.68 for the polarization vectors of (001) directions, respectively, which reveals the fact that the compound 1 and 2 might be good charge transport materials. The reflectivities of the compound 1 and 2 are 0.64 and 0.45 revealing that the compound 2 might be more efficient material for organic photovoltaic (OPV) applications. The results of the refractive index improved by doping the strong electron withdrawing groups (EWGs) shows that the compound 2 might be good refractor of the photon as compared to compound 1. The calculated values for static second-order polarizability are 3498 and 10464 a. u. and for frequency dependent second harmonic generations are 2557 and 6429 a. u. for compound 1 and 2, respectively, which indicates their significant potential for possible nonlinear optical applications.     

沉积氧气压力对纳米晶硅光致发光的影响

用脉冲激光（Nd：YAG激光）沉积技术在硅基上沉积富硅SiO2薄腊（SiOx，x〈2），沉积时氧气压力分别为1．33，2．66，3．99，5．32，6．65，7．98Pa，膜的厚度约为300nm。随后，在氩（Ar）气中1000℃的温度下对沉积的SiOx薄膜进行热退火处理30min，使在SiO2薄膜中生长出硅纳米晶。用光谱分析仪分析其在室温下的光致发光（PL）光谱时发现，随着沉积氧气压力的增强，峰值波长在减小（即蓝移），表明纳米晶硅颗粒在减小；同时，在本研究中的制作条件下，PL强度与沉积氧气压力有较强的依存关系，在2．66-3．99Pa的氧气压力条件下沉积制作的试样，得到最大的PL强度。     

Structural, electronic, and magnetic properties of heterofullerene C(58)Si with odd number of atoms and a near planar tetracoordinate Si atom

Density functional calculations and minimization techniques have been employed to characterize the structural and electronic properties of [5,6]-heterofullerene-C₅₈Si-C_2v. Since it has odd number of atoms and a near planar tetracoordinate Si atom on the skeleton of the cage, it has odd number of atoms assembling a cage and is a novel molecule. Vibrational frequencies of the molecule have been calculated at the B3LYP/6-31G* level of theory. The absence of imaginary vibrational frequency confirms that the molecule corresponds to a true minimum on the potential energy hypersurface. Sixteen ¹³C nuclear magnetic resonance (NMR) spectral signals of C₅₈Si are characterized, and its heat of formation was estimated in this work.     

Impact of alcohol additives concentration on etch rate and surface morphology of (100) and (110) Si substrates etched in KOH solutions

The influence of alcohol concentration on etch rate and surface morphology of (100) and (110) Si planes was investigated in this paper. The etching processes were carried out in KOH solutions with different concentrations of isopropanol and butanols. The etch rate minima versus alcohol concentration were observed for all the alcohols used in the experiments. Furthermore, close to the concentrations of etch rate minima, the smooth (110) planes were obtained. However, the (100) surfaces were covered with hillocks at these concentrations. Based on the surface tension measurements and literature reports, the explanation of appearance of the etch rate minimum was suggested. In the proposed model, the adsorption maximum corresponds to the complete formation of an alcohol monolayer on Si surface and, consequently, to the etch rate minimum. At higher concentrations of alcohol, the monolayer disappears and the etch rate increases.     

Electronic,electrical and thermodynamic properties of Ca5Si3 by first principles calculations and low temperature experimental techniques

A combined experimental and computational study of the Ca₅Si₃ phase is presented. Its’ electronic structure and lattice stability are investigated by first principles methods: four different crystal lattices have been investigated by means of density functional theory (DFT) calculations and pseudopotentials within the generalized-gradient approximation using the VASP code. The Ca₅Si₃ phase is predicted to undergo an high pressure transition: the lattice transition tI32(Cr₅B₃-type) → tI32(W₅Si₃-type) has been predicted by DFT to occur at 14.9 GPa. The electronic and band structure of the tI32 Cr₅B₃-type lattice is calculated and discussed. The Ca₅Si₃ phase ground state structure is predicted to be a metal with a peaked density of states below the Fermi energy and a sharp minimum right above it. Experimentally the low temperature resistivity and heat capacity of the Ca₅Si₃ phase have been measured between 2 and 300 K and discussed in view of our computational predictions and available literature. The Ca₅Si₃ tI32(Cr₅B₃-type) standard pressure polymorph exhibits a metallic temperature dependence of the electric conductivity in agreement with the DFT predictions.     

等离子体和反应离子刻蚀硅的各向异性 及均匀性实验研究

在反应离子刻蚀(RIE)及等离子体刻蚀(PE)设备中,分别采用CF_4,SF_6,NF_3和C_7F_(14),腐蚀剂气体,对(100)Si进行刻蚀.研究了工艺条件对刻蚀各向异性及均匀性的影响.结果表明,RIE的各向异性与均匀性均优于PE.RIE的各向异性值A与刻蚀气体中的添加剂成份有关,添加20%Ar时A最大值为5.4;添加20%C_2F_5Cl时,A值可高达10以上.在RIE中,CF_4和NF_3,的刻蚀均匀性优于SF_6,最佳刻蚀均匀性平均值优于5%,添加剂对刻蚀均匀性没有明显的影响.而PE显示各向同性的刻蚀特征,均匀性约为16.5%.并对各向异性及均匀性的起因作了解释.     

Tuning of electrical and optical properties of organic LEDs using combinatorial device fabrication

The capabilities of combinatorial methods are presented in order to get a detailed understanding of the electrical and optical properties of organic light‐emitting devices (OLEDs), to optimize their performance, and to provide reliable data for device modeling. We show results on multilayer OLEDs ranging from the conventional copper‐phthalocyanine (CuPc)/N,N′di‐(naphtalene‐1‐yl)‐N,N′‐diphenyl‐benzidine (NPB) and tris‐(8‐hydroxy‐quinolinato)aluminum (Alq) tri‐layer device to double‐doped deep‐red‐emitting OLEDs.     

基于法拉第磁光效应的光学电流传感器电气特性研究

研究了基于法拉第磁光效应的光学电流传感器的电气特性。根据马吕斯定律,仿真分析了起偏镜与检偏镜光轴之间的夹角、交变电流引起的交变法拉第旋转角的幅值对此种光学电流传感器交流响应波形的影响,以及响应的幅值特性和频率特性。通过对此种光学电流传感器电气特性的研究,为实验中出现的问题提供了解决思路,同时也为磁光介质的参数确定提供了依据。仿真和部分实验结果表明此种光学电流传感器在合适参数下具有较好的响应波形以及幅值、频率特性。     

The electrical and optical properties of AZO thin film under different post-annealing temperatures

In this study, the Aluminum element doped zinc oxide (Al:ZnO) thin film was deposited on the Corning glass substrate by RF magnetron sputtering technology and annealing treatment. After sputtering, all thin films are then annealed on nitrogen atmosphere and temperature of 300, 500 and 550 °C, respectively. The structural, electric and optical characteristics were then investigated. All films illustrate strong (002) for ZnO and (335) for Al preferential orientation by using XRD analysis. The lower resistivity can be observed at nitrogen annealing and temperature of 400 °C. The transmittance property of AZO thin film exhibited an excellent transparency in the visible light range. The transmittance reached to nearly 81.4 % for all Al:ZnO film. It can be clearly observed that the grain size of AZO thin film is very uniform by utilizing SEM technology.     

基于光纤辐射效应的温度传感器工作波长研究

辐射后光纤的损耗值显著增加,这种现象被称为光纤辐射致衰减（ RIA）效应。基于RIA效应的温度特性,搭建了一种新型的光纤温度传感器。为选择合适的传感器工作波长,基于位形坐标模型理论对锗磷（ Ge/P）共掺杂光纤在825～1500 nm范围内的RIA谱特性进行了研究,发现短波段光纤RIA对温度的依赖性明显优于长波段。选用了常见的850 nm普通单模光纤作为敏感光纤,搭建光纤温度传感器,最后对所搭建温度传感器的性能指标做出了评估。