Electrical properties of hafnium silicate films obtained from a single-source MOCVD precursor

In the present work, the potential of hafnium silicate (Hf_xSi_yO₂) films as an alternative gate dielectric to SiO₂ for future technology generations is demonstrated. Thermally stable Hf_xSi_yO₂ films are deposited from a single-source MOCVD precursor. I–V and C–V measurement data are presented and effects of post-deposition annealing on electrical properties are discussed. A 900 °C O₂-anneal shows best results in terms of leakage current characteristics and is, therefore, intensively investigated.     

Tuning the dielectric properties of hafnium silicate films

The influence of Si concentration in hafnium silicate dielectrics on thermal stability and dielectric permittivity was analyzed. A phase diagram was developed using GIXRD and FTIR measurement. The stabilization of the “higher-k” cubic/tetragonal phase for annealing temperatures up to 1000 °C with a steady increase in capacitance was demonstrated for Hf_0.94Si_0.06O₂ films. It was also shown that the stabilization of nano-crystalline Hf_0.80Si_0.20O₂ films can be realized for annealing temperatures up to 900 °C. The influence of TiN electrodes on the dielectric constant and the leakage current characteristic was also investigated. A permittivity increase for annealing temperatures up to 1000 °C without degradation of leakage current was shown.     

Electrical characterization of hafnium oxide and hafnium-rich silicate films grown by atomic layer deposition

An electrical characterization comparative analysis between Al/HfO₂/n-Si and Al/Hf-Si-O/n-Si samples has been carried out. Hafnium-based dielectric films have been grown by means of atomic layer deposition (ALD). Interface quality have been determined by using capacitance–voltage (C–V), deep level transient spectroscopy (DLTS) and conductance transient (G-t) techniques. Our results show that silicate films exhibit less flat-band voltage shift and hysteresis effect, and so lower disordered induced gap states (DIGS) density than oxide films, but interfacial state density is greater in Hf–Si–O than in HfO₂. Moreover, a post-deposition annealing in vacuum under N₂ flow for 1 min, at temperatures between 600 and 730 °C diminishes interfacial state density of Hf–Si–O films to values measured in HfO₂ films, without degrade the interface quality in terms of DIGS.     

Electrical properties of tellurium thin films

Semiconducting properties of evaporated tellurium thin films, in the thickness range of 100 to 400 Å, are studied and correlated with observed structural properties. It is found that less-than-monolayer gold films can act as nucleation sites and stimulate the growth of large crystallites in deposited Te films. The Au-nucleated Te films are preferentially oriented with the c axis in the substrate plane and have crystallite diameters ranging from 2 to 5 µm. Hall mobilities as high as 250 cm²/V ċ s are observed in 400-Å Au-nucleated films with 5-µm crystallites. These large-grain films exhibit a temperature dependence for mobility of the form µ ∼ T^3/2between 85°K and 250°K, while the carrier concentrations in the films do not change appreciably with temperature. Transconductances greater than 1000 µmhos are achieved for Au-nucleated Te thin-film transistors with 3-mil channels (operating with a saturated drain current of 1 mA). Several devices exhibit field-effect mobilities greater than 100 cm²/V ċ s, a value consistent with the observed Hall mobilities for similar films. Transconductance measurements indicate that Te thin-film transistor (TFT) instabilities result primarily from hole trapping at the Te-insulator interface. It is possible to alter the threshold voltage of Te TFTs by applying a gate bias at room temperature. Improved stability (changes in V0less than 50 mV in 1 h) is observed at 77°K. From the observed changes in threshold, a lower limit of the trapping-state density at the surface is inferred to be 5×10¹²traps/cm². The surface-state density at the Te-SiO interface is estimated to be less than 6×10¹²surface states/cm²ċ eV as determined from capacitance and conductance measurements.     

硅基铁电薄膜的制备与电性能研究

用溶胶－凝胶（Ｓｏｌ－Ｇｅｌ）方法制备了有ＰｂＴｉＯ３（ＰＴ）过渡层的硅基Ｐｂ（Ｚｒ０．５３Ｔｉ０．４７）Ｏ３（ＰＺＴ）铁电薄膜，顶电极和底电极分别为溅射的金属钛铂层和低阻硅。在低温退火条件下得到了晶化很完善的铁电薄膜，测试结果表明有ＰＴ过渡层的铁电薄膜具有良好的铁电和介电性能。     

Electrical properties of zinc oxide sputtered thin films

ZnO thin films were deposited on silicon substrate by rf magnetron sputtering from metallic zinc target. The electrical properties of ZnO are currently being studied. In this work, measurements of the ac conductivity properties of ZnO sandwich structures with silver and platinum electrodes are reported. The frequency dependence of both the ac conductivity and dielectric constant of thin films of ZnO have been investigated in the frequency range 5 kHz-13 MHz. It is shown that the total ac conductivity σ(ω), obeys the equation σ(ω)=Aω^S where s is an index which increases with frequency and decreases with temperature. It appears that for ZnO films, the conduction mechanism is thermally activated and both the overlap large polaron tunnelling and the correlated barrier-hopping of charge carrier over localized states fit the experimental data. The dielectric constant, ε_r, lies in the range 8-9 at room temperature and is independent of the frequency in the dielectric thin films.     

Electrical and structural properties of cadmium selenide thin film transistors

Stable thin film transistors based on cadmium senenide and silicon dioxide have been prepared. The degree of stability implies a decay of only 10% in drain current in 100 years of continuous d.c. operation. The decay is solely due to tunnelling of electrons into insulator traps and has a logarithmic time dependence. The devices have field effect mobilities up to 140 cm². Volt^?1 sec^?1, switching ratios in the range 10⁵–10⁶, and good reproducibility. The CdSe films contain the hexagonal structure and grain growth occurs during anneal. Grain size and distribution are reproducible from run to run.     

Electrical and structural properties of pulse laser-annealed polycrystalline silicon films

Doped epitaxial films of Si on single-crystal high-resistivity Si substrates have been prepared using ion implantation and Q-switched ruby laser annealing of LPCVD polycrystalline Si layers. Films, doped with B or As in the range 10¹⁷to 5 × 10²⁰cm^-3were studied by the measurement of their resistivities, Hall mobilities, and doping density profiles. The good film quality achieved permitted the fabrication of p-channel MOS transistors which, through measurements of threshold voltage and transconductance, yielded additional data on the surface mobility and the integrity of the Si-SiO2interface. The electrical properties of the films compared favorably with those of similarly doped single-crystal material, and transmission electron microscopy was used to confirm the good structural quality of the epitaxial growth.     

Electrical properties of silver Schottky contacts to ZnO thin films

ZnO thin films are deposited on Al/Si substrates by the pulsed laser deposition （PLD） method. The XRD and SEM images of films are examined. Highly c-axis oriented ZnO thin films which have uniform compact surface morphology are fabricated. The size of surface grains is about 30 nm. The Schottky barrier ultraviolet detectors with silver Schottky contacts are made on ZnO thin films. The current-voltage characteristics are measured. The ideality contact factor between Ag and ZnO film is 1.22, while the barrier height is 0.908 e V. After annealing at 600 ℃ for 2h, the ideality factor is 1.18 and the barrier height is 0.988 eV. With the illumination of 325 nm wavelength UV-light, the photocurrent-to-dark current ratios before and after annealing are 140.4 and 138.4 biased at 5 V, respectively. The photocurrents increase more than two orders of magnitude over the dark currents.     

Electrical measurements of dielectric properties of molybdenum-doped zinc oxide thin films

Effects of molybdenum element content on electrical conductivity of ZnO sprayed thin films were investigated using the impedance spectroscopy method in the frequency ranging from 5 Hz to 13 MHz for temperature lying in 300–475 °C domain. It is observed that AC conductivity is a power law. The values of dielectric constants ε₁ and ε₂ were found to decrease with frequency and increase with temperature. The activation energy determined from the plot of both DC conductivity and the hopping frequency with 1000/T shows that the hopping conduction is the dominant mechanism. Also, experimental data of DC conductivity were analyzed using the small polaron hopping model. The impedance analysis of undoped ZnO and Mo-doped ZnO (1% and 2%) shows only one semicircle implying the response originated from a single capacitive element corresponding to the bulk grains. However, the same analysis for ZnO:Mo (3% ) shows two semicircles which proves the existence of grain boundaries. Finally, analyses of polaron hopping mechanism and Urbach tailing allow some explanations of these transport phenomena. This study shows an effective variation of electrical measurements of Mo-doped ZnO films in terms of temperature leading to possible use of such films as gas sensors.     

Electrical properties of Copper（Ⅱ） phthalocyanine derivative thin films

Phthalocyanine (Pc) or Metallophthalocyanines (MPc) are aromatic compounds or complexes with semiconducting properties. Besides, they are chemically and thermally stable with the potential to be used as the hole transport layers, or injection layers in th…     

Investigation of structural and optoelectronic properties of annealed nickel phthalocyanine thin films

Thin films of nickel phthalocyanine (NiPc) were prepared by thermal evaporation and the effects of annealing temperature on the structural and optical properties of the samples were studied using different analytical methods. Structural analysis showed that the grain size and crystallinity of NiPc films improved as annealing temperature increased from 25 to 150 °C. Also, maximum grain size (71.3 nm) was obtained at 150 °C annealing temperature. In addition, NiPc films annealed at 150 °C had a very smooth surface with an RMS roughness of 0.41 nm. Optical analysis indicated that band gap energy of films at different annealing temperatures varied in the range of 3.22–3.28 eV. Schottky diode solar cells with a structure of ITO/PEDOT:PSS/NiPc/Al were fabricated. Measurement of the dark current density–voltage (J–V) characteristics of diodes showed that the current density of films annealed at 150 °C for a given bias was greater than that of other films. Furthermore, the films revealed the highest rectification ratio (23.1) and lowest barrier height (0.84 eV) demonstrating, respectively, 23% and 11% increase compared with those of the deposited NiPc films. Meanwhile, photoconversion behavior of films annealed at 150 °C under illumination showed the highest short circuit current density (0.070 mA/cm²) and open circuit voltage of (0.55 V).     

Theoretical investigation of the electronic and structural properties of AlN thin films

Studying the electronic and structural properties of AlN thin films is an important problem because such films are widely used as a buffer layer when growing GaN-based semiconductor heterostructures on Si substrates. In this paper, we carry out a theoretical investigation of the properties of an Al-terminated AlN(0001) surface in the framework of the density functional theory. Ab initio calculations allow us to analyze the effect of the in-plane lattice strain on the energy of this surface. It is shown that compressive strain causes a decrease in the AlN(0001) surface energy, while tensile strain leads to its increase. Knowing the surface energy values allows us to evaluate the stress of the surface under investigation. In addition, the curvature of the AlN surface is calculated for various AlN film thicknesses in the case of free growth. The obtained values of the surface curvature are in close agreement with the known experimental results.     

衬底温度对CZTSSe薄膜结构特性的影响

采用热蒸发法制备铟锌锡硫(CZTSSe)薄膜。采用低 温一步 法在300℃衬底温度下制备CZTSSe薄膜;采用两步法,即在衬底温度 分别为300℃制备CZTSSe 薄膜;将衬底温度设定为480℃不变,一步蒸发沉积CZTSSe薄膜。通 过对X射线衍射(XRD)、 扫描电镜(SEM)、拉曼谱对比发现,在300℃低温下一步法和300℃ 、480℃两 步法沉积的薄膜表面粗糙,碎小晶粒较多;在480℃一步高温法制备 的薄膜表面平整, 晶粒大小均匀,3个衍射峰的半高峰宽变窄,薄膜的结晶质量得到 改善,且没有发现其它杂相的拉曼特征峰,沉积出适合作为制备CZTSSe薄膜太阳电池的 吸收层。     

Annealing temperature dependent structural and optical properties of electrodeposited CdSe thin films

Cadmium selenide films were synthesized using simple electrodeposition method on indium tin oxide coated glass substrates. The synthesized films were post annealed at 200 °C, 300 °C and 400 °C. X-ray diffraction of the films showed the hexagonal structure with crystallite size <3 nm for as deposited films and 3–25 nm for annealed films. The surface morphology of films using field emission scanning electron microscopy showed granular surface. The high resolution transmission electron microscopy of a crystallite of the film revealed lattice fringes which measured lattice spacing of 3.13 Å corresponding to (002) plane, indicating the lattice contraction effect, due to small size of CdSe nanocrystallite. The calculation of optical band gap using UV–visible absorption spectrum showed strong red-shift with increase in crystallite size, indicating to the charge confinement in CdSe nanocrystallite.     

Effects of substrate temperature on electrical and structural properties of copper thin films

This paper addresses the effects of substrate temperature on electrical and structural properties of dc magnetron sputter-deposited copper (Cu) thin films on p-type silicon. Copper films of 80 and 500 nm were deposited from Cu target in argon ambient gas pressure of 3.6 mTorr at different substrate temperatures ranging from room temperature to 250 °C. The electrical and structural properties of the Cu films were investigated by four-point probe and atomic force microscopy. Results from our experiment show that the increase in substrate temperature generally promotes the grain growth of the Cu films of both thicknesses. The RMS roughness as well as the lateral feature size increase with the substrate temperature, which is associated with the increase in the grain size. On the other hand, the resistivity for 80 nm Cu film decreases to less than 5 μΩ-cm at the substrate temperature of 100 °C, and further increase in the substrate temperature has not significantly decreased the film resistivity. For the 500 nm Cu films, the increase in the grain size with the substrate temperature does not conform to the film resistivity for these Cu films, which show no significant change over the substrate temperature range. Possible mechanisms of substrate-temperature-dependent microstructure formation of these Cu films are discussed in this paper, which explain the interrelationship of grain growth and film resistivity with elevated substrate temperature.     

Electrical properties of carbon nitride thin films: Role of morphology and hydrogen content

The influence of hydrogen content and ambient humidity on the electrical properties of carbon nitride (CN_x) films deposited by reactive magnetron sputtering from a graphite target in Ar discharges mixed with N₂ and H₂ at a substrate temperature of 350°C have been investigated. Carbon films deposited in pure Ar exhibit a dark resistivity at room temperature of ∼4 × 10⁻² Ωcm, while the resistivity is one order of magnitude lower for CN_0.25 films deposited in pure N₂, due to their denser morphology. The increasing H₂ fraction in the discharge gas leads to an increased resistivity for all gas mixtures. This is most pronounced for the nitrogen-free films deposited in an Ar/H₂ mixture, where the resistivity increases by over four orders of magnitude. This can be related to a decreased electron mobility as H inhibits the formation of double bonds. After exposure to air, the resistivity increases with time through two different diffusion regimes. The measured electrical properties of the films are related to the apparent film microstructure, bonding nature, and ambient humidity.     

溶液PH值对CdS薄膜结构特性的影响

采用化学水浴沉积(CBD)工艺在玻璃衬底上制 备CdS薄膜,研究溶液PH值对CdS 薄膜结构特性的影响。薄膜的厚度、组份、晶相结构和表观形貌分别由台阶仪、X射线荧光 光谱(XRF)、X射线衍射(XRD)和场发射扫描电子显微镜(FESEM)来表征。溶液的 PH值为11.26、 11.37和11.48时,CdS薄膜的晶相以六方相为主,薄膜的厚度先增大后减小; PH值为11.62、11.66时,薄膜的晶相以立方相为主,薄 膜的厚度进一步减小。同时,随着溶液PH值 增大,CdS薄膜的晶格常数也逐渐增大。两种晶相的CdS薄膜缓冲层与CIGS薄膜分别构成异 质 对形成异质结时的晶格失配分别为32.297%和1.419%,界面态密度分别为2.792×10¹⁴和8.507×10¹²,因此高效CIGS薄 膜太阳电池更需要立方相的CdS薄膜。     

Thickness dependent structural and optical properties of In/Te bilayer thin films

In_xTe_y thin films have been prepared from In/Te bilayer by sequential thermal evaporation. The samples were analyzed by x-ray diffraction (XRD), optical transmittance spectra and scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDX) in order to investigate structural, optical properties, surface morphology and elemental composition of the prepared films. XRD spectra reveal that all films exhibit mixed phases of In₂Te₃ and In₂Te₅. Increase in grain size with film increase in thickness was observed. The surface was highly porous as observed by SEM analysis. Band gap energy of In_xTe_y system is found to decrease with increase in film thickness.     

ZnS上HfON保护膜及增透膜系的制备和性能研究

用氮氧化铪薄膜作为CVDZnS衬底的保护膜、由YbF3和ZnS组成的增透膜系分别在CVDZnS的两面制备了保护膜和增透膜,研究了镀膜前后CVDZnS在8~12 μm波段的光学性能,单面镀制增透膜之后CVDZnS在此波段的平均透过率由未镀膜前的74%提高到了82%,峰值透过率大于83.5%。在CVDZnS上镀制HfON保护膜后,其8~12 μm波段透过率没有明显的降低,同时硬度测试表明HfON薄膜的硬度约为11.6 GPa,远大于衬底CVDZnS的硬度。胶带实验和泡水试验表明,制备的保护膜和增透膜均和衬底有