Studies of Laser-induced-MOCVDZinc Oxide Films

hin films of ZnO were prepared using the double photobeams ultraviolet laserinduced-metallorganic chemical vapour deposition (MOCVD)technique. The struc-ture and transparent photoconductive properties of these films were investigated us-ing X-ray diffraction (XRD) , reflecting electron diffraction (RED) .scanning elec-tron microscopy (SEM) and ultraviolet visible absorption spectrometry (UV) .Theexperiments showed that the technique produced superior quality films of polycrys-tal ZnO_(1-x) (the O-vacancies in the ZnO lattice) , and possessed higher depositionrate, lower growth temperature conipared with CVD or MOCVD technique and thethin films had far better transparent photoconductive properties than tliose grownby the conventional CVD or MOCVD technique.

Influence of the sputtering pressure on the properties of transparent conducting zirconium-doped zinc oxide films prepared by RF magnetron sputtering

Transparent conducting zirconium-doped zinc oxide films with high transparency and relatively low resistivity have been successfully prepared on water-cooled glass substrate by radio frequency magnetron sputtering at room temperature. The Ar sputtering pressure was varied from 0.5 to 3 Pa. The crystallinity increases and the electrical resistivity decreases when the sputtering pressure increases from 0.5 to 2.5 Pa. The cystallinity decreases and the electrical resistivity increases when the sputtering pressure increases from 2.5 to 3 Pa. When the sputtering pressure is 2.5 Pa, it is obtained that the lowest resistivity is 2.03 x 10^-3Ω .cm with a very high transmittance of above 94%. The deposited films are polycrystalline with a hexagonal structure and a preferred orientation perpendicular to the substrate.

Preparation and Characterization of Transparent Conductive Zinc Doped Tin Oxide Thin Films Prepared by Radio-frequency Magnetron Sputtering

High transparent and conductive thin films of zinc doped tin oxide （ZTO） were deposited on quartz substrates by the radio-frequency （RF） magnetron sputtering using a 12 wt% ZnO doped with 88 wt% SnO2 ceramic target.The effect of substrate temperature on the structural,electrical and optical performances of ZTO films has been studied.X-ray diffraction （XRD） results show that ZTO films possess tetragonal rutile structure with the preferred orientation of （101）.The surface morphology and roughness of the films was investigated by the atomic force microscope （AFM）.The electrical characteristic （including carrier concentration,Hall mobility and resistivity） and optical transmittance were studied by the Hall tester and UV- VIS,respectively.The highest carrier concentration of -1.144×1020 cm-3 and the Hall mobility of 7.018 cm2（V ·sec）-1 for the film with an average transmittance of about 80.0% in the visible region and the lowest resistivity of 1.116×10-2 Ω·cm were obtained when the ZTO films deposited at 250 oC.

Double-layer indium doped zinc oxide for silicon thin-film solar cell prepared by ultrasonic spray pyrolysis

Indium doped zinc oxide （ZnO：In） thin films were prepared by ultrasonic spray pyrolysis on corning eagle 2000 glass substrate. 1 and 2 at.% indium doped single-layer ZnO：In thin films with different amounts of acetic acid added in the initial solution were fabricated. The 1 at.% indium doped single-layers have triangle grains. The 2 at.% indium doped single-layer with 0.18 acetic acid adding has the resistivity of 6.82 × 10^-3 Ω. cm and particle grains. The doublelayers structure is designed to fabricate the ZnO：In thin film with low resistivity （2.58 × 10^-3 Ω. cm） and good surface morphology. It is found that the surface morphology of the double-layer ZnO：In film strongly depends on the substratelayer, and the second-layer plays a large part in the resistivity of the doublewlayer ZnO：In thin film. Both total and direct transmittances of the double-layer ZnO：In film are above 80% in the visible light region. Single junction a-Si：H solar cell based on the double-layer ZnO：In as front electrode is also investigated.

Structural,Morphological and Electrical Properties of In-Doped Zinc Oxide Nanostructure Thin Films Grown on p-Type Gallium Nitride by Simultaneous Radio-Frequency Direct-Current Magnetron Co-Sputtering

Zinc oxide （ZnO） is one of the most promising and frequently used semiconductor materials. In-doped nanos- tructure ZnO thin films are grown on p-type gallium nitride substrates by employing the simultaneous rf and dc magnetron co-sputtering technique. The effect of In-doping on structural, morphological and electrical properties is studied. The different dopant concentrations are accomplished by varying the direct current power of the In target while keeping the fixed radio frequency power of the ZnO target through the co-sputtering deposition technique by using argon as the sputtering gas at ambient temperature. The structural analysis confirms that all the grown thin films preferentially orientate along the c-axis with the wurtzite hexagonal crystal structure without having any kind of In oxide phases. The presenting Zn, 0 and In elements＇ chemical compositions are identified with EDX mapping analysis of the deposited thin films and the calculated M ratio has been found to decrease with the increasing In power. The surface topographies of the grown thin films are examined with the atomic force microscope technique. The obtained results reveal that the grown film roughness increases with the In power. The Hall measurements ascertain that all the grown films have n-type conductivity and also the other electrical parameters such as resistivity,mobility and carrier concentration are analyzed.

Low-Frequency Noise in Amorphous Indium Zinc Oxide Thin Film Transistors with Aluminum Oxide Gate Insulator

Low-frequency noise（LFN） in all operation regions of amorphous indium zinc oxide（a-IZO） thin film transistors（TFTs） with an aluminum oxide gate insulator is investigated. Based on the LFN measured results, we extract the distribution of localized states in the band gap and the spatial distribution of border traps in the gate dielectric,and study the dependence of measured noise on the characteristic temperature of localized states for a-IZO TFTs with Al2 O3 gate dielectric. Further study on the LFN measured results shows that the gate voltage dependent noise data closely obey the mobility fluctuation model, and the average Hooge＇s parameter is about 1.18×10^-3.Considering the relationship between the free carrier number and the field effect mobility, we simulate the LFN using the △N-△μ model, and the total trap density near the IZO/oxide interface is about 1.23×10^18 cm^-3eV^-1.

Creation and research of the SAW transducer with a single-phase grid and a piezoelectric zinc oxide film

A method for obtaining a new type of surface acoustic wave(SAW)transducer operating at double frequency with a single-phase closed-loop lattice and a piezoelectric zinc oxide film is developed and experimentally investigated.A method for calculating such a transducer has been developed,its equivalent circuit has been compiled,taking into account propagation losses,losses in the metal film and the inductance of the connecting wires.When the frequency is doubled,the SAW attenuation per unit length increases.

High-throughput fabrication and semi-automated characterization of oxide thin film transistors

High throughput experimental methods are known to accelerate the rate of research,development,and deployment of electronic materials.For example,thin films with lateral gradients in composition,thickness,or other parameters have been used alongside spatially-resolved characterization to assess how various physical factors affect the material properties under varying measurement conditions.Similarly,multi-layer electronic devices that contain such graded thin films as one or more of their layers can also be characterized spatially in order to optimize the performance.In this work,we apply these high throughput experimental methods to thin film transistors(TFTs),demonstrating combinatorial channel layer growth,device fabrication,and semi-automated characterization using sputtered oxide TFTs as a case study.We show that both extrinsic and intrinsic types of device gradients can be generated in a TFT library,such as channel thickness and length,channel cation compositions,and oxygen atmosphere during deposition.We also present a semi-automated method to measure the 44 devices fabricated on a 50 mm×50 mm substrate that can help to identify properly functioning TFTs in the library and finish the measurement in a short time.Finally,we propose a fully automated characterization system for similar TFT libraries,which can be coupled with high throughput data analysis.These results demonstrate that high throughput methods can accelerate the investigation of TFTs and other electronic devices.

Fabrication and Magnetic Properties of Highly Oriented ZnO:Eu Films by Sol-Gel Process

A series of Eu-doped ZnO films were prepared by a sol-gel method. Precursor and films were characterized by thermal analysis (TG-DTA), X-ray diffraction (XRD), scanning electron microscope (SEM), UV-vis spectra, as well as the magnetism measurement. The wurtzite structure of obtained films presents an extreme high c-orientation character. The film susceptibility resembles a Curie-Weiss behavior at high temperature, and presents an obvious enhancement at low temperature, indicating the presence of antiferromagnetic interactions in the Zn0.9Eu0.1O films.

MICROSTRUCTURE AND PROPERTIES OF ANNEALED ZnO THIN FILMS DEPOSITED BY MAGNETRON SPUTTERING

ZnO thin films were deposited on a glass substrate by dc (direct current) and rf (radio frequency) magnetron sputtering. Post-deposition annealing was performed in different atmospheres and at different temperatures. The correlation of the annealing conditions with the microstructure and properties of the ZnO films wer e investigated by ultraviolet-visible spectroscopy, X-ray diffraction, conductiv ity measurement and scanning electron microscopy. Only the strong 002 peak could be observed by X-ray diffraction. The post-deposition annealing of ZnO films wa s found to alter the film's microstructure and properties, including crystallini ty, porosity, grain size, internal stress level and resistivity. It was also fou nd that after annealing, the conductivity of poorly conductive samples often imp roved. However, annealing does not improve the conductivity of samples with high conductivity prior to annealing. The resistivity of as-grown films can be decre ased from 102 to 10-4Ω·cm after annealing in nitrogen. To explain the effects of annealing on the conductivity of ZnO, it is believed that annealing may alter the presence and distribution of oxygen defects, reduce the lattice stress, cau se diffusion, grain coarsening and recrystallization. Annealing will reduce the density of grain boundaries in less dense films, which may decrease the resistiv ity of the films. On the other hand, annealing may also increase the porosity of thin films, leading to an increase in resistivity.

Facile Synthesis of 3D Porous Flower-like ZnO Micro/nanostructure Films and Their Photocatalytic Performance

3D porous flower-like ZnO micro/nanostructure films grown on Ti substrates are synthesized via a very facile electrodeposition technique followed by heat treatment process. The ZnO architecture is assembled with ultra thin sheets, which consist of numbers of nanoparticles and pores, and the size of the nanoparticles can be controlled by adjusting the electrodepo- sition time or calcination temperature. It is worth noting that this synthetic method can provide an effective route for other porous metal oxide nanostructure films. Moreover, the photocatalytic performance shows the porous ZnO is an ideal photocatalyst.

Dual Manipulation of Ferromagnetism in Co-Doped ZnO Thin Films by Surfactant and n-Type Carriers

We present a conceptually-new approach “dual manipulation effect” using the surfactant passivation and the electron carrier doping for mediating intrinsic ferromagnetism in Codoped ZnO dilute magnetic semiconductor (DMS) thin films. The first-principles calculations show that the surface passivation by hydrogen serves as a magnetism switch for the Co-O-Co magnetic coupling at the surface of the thin film, and thus can control the spin polarization of the doped Co atoms. Meanwhile, the electron carrier doping can further function as an effective layerlike ferromagnetism mediator for the underneath layer. The dual manipulation effect sheds light on the essential magnetism origin of n-type Co:ZnO DMS thin films, and may be used as an alternative strategy for enhancing the ferromagnetism in other n-type DMS oxides thin films.

Influence of the distance between target and substrate on the properties of transparent conducting Al-Zr co-doped zinc oxide thin films

Highly transparent and conducting Al-Zr co-doped zinc oxide （ZAZO） thin films were successfully prepared on glass substrate by direct current （DC） magnetron sputtering at room temperature. The distance between target and substrate was varied from 45 to 70 mm. All the deposited films are polycrystalline with a hexagonal structure and have a preferred orientation along the c-axis perpendicular to the substrate. The crystallinity increases obviously and the electrical resistivity decreases when the distance between target and substrate decreases from 70 to 50 mm. However, as the distance decreases further, the crystallinity decreases and the electrical resistivity increases. When the distance between target and substrate is 50 ram, it is found that the lowest resistivity is 6.9 × 10^-4Ω cm. All the deposited films show a high average transmittance of above 92% in the visible range.

Effects of annealing rate and morphology of sol–gel derived ZnO on the performance of inverted polymer solar cells

The effects of annealing rate and morphology of sol–gel derived zinc oxide （ZnO） thin films on the performance of inverted polymer solar cells （IPSCs） are investigated. ZnO films with different morphologies are prepared at different annealing rates and used as the electron transport layers in IPSCs. The undulating morphologies of ZnO films fabricated at annealing rates of 10 ℃/min and 3 ℃/min each possess a rougher surface than that of the ZnO film fabricated at a fast annealing rate of 50 ℃/min. The ZnO films are characterized by atomic force microscopy （AFM）, optical transmittance measurements, and simulation. The results indicate that the ZnO film formed at 3 ℃/min possesses a good-quality contact area with the active layer. Combined with a moderate light-scattering, the resulting device shows a 16% improvement in power conversion efficiency compared with that of the rapidly annealed ZnO film device.

Modified textured surface MOCVD-ZnO:B transparent conductive layers for thinfilm solar cells

Modified textured surface boron-doped ZnO （ZnO：B） transparent conductive layers for thin-film solar cells were fabricated by low-pressure metal organic chemical vapor deposition （LP-MOCVD） on glass substrates. These modified textured surface ZnO：B thin films included two layers. The first ZnO：B layer, which has a pyramid- shaped texture, was deposited under conventional growth conditions, and the second layer, which has a sphere- like structure, at a relatively lower growth temperature. Typical bi-layer ZnO：B thin films exhibit a high electron mobility of 27.6 cm^2/（V.s） due to improved grain boundary states. For bi-layer ZnO：B, the haze value increases and the total transmittance decreases with the increasing film thickness of the second modification layer. When applied in hydrogenated microcrystalline silicon （μc-Si：H） thin-film solar cells, the modified textured surface ZnO：B layers present relatively higher conversion efficiency than conventional ZnO：B films.

Thickness dependence of the properties of transparent conducting ZnO:Zr films deposited on flexible substrates by RF magnetron sputtering

Transparent conducting zirconium-doped zinc oxide （ZnO：Zr） thin films with high transparency, low resistivity and good adhesion were successfully prepared on water-cooled flexible substrates （polyethylene glycol terephthalate, PET） by RF magnetron sputtering. The structural, electrical and optical properties of the films were studied for different thicknesses in detail. X-ray diffraction （XRD） and scanning electron microscopy （SEM） revealed that all the deposited films are polycrystalline with a hexagonal structure and a preferred orientation perpendicular to the substrate. The lowest resistivity achieved is 1.55 × 10-3 Ω·cm for a thickness of 189 nm with a Hall mobility of 17.6 cm2/（V·s） and a carrier concentration of 2.15×1020 cm-3. All the films present a high transmittance of above 90% in the wavelength range of the visible spectrum.

High conductive and transparent AI doped ZnO films for a-SiGe：H thin film solar cells

Al doped zinc oxide （AZO） films were prepared by mid-frequency magnetron sputtering for silicon （Si） thin film solar cells. Then, the influence of deposition parameters on the electrical and optical properties of the films was studied. Results showed that high conductive and high transparent AZO thin films were achieved with a minimum resistivity of 2.45 × 10^-4 Ω·cm and optical transmission greater than 85% in visible spectrum region as the films were deposited at a substrate temperature of 225℃ and a low sputtering power of 160 W. The optimized films were applied as back reflectors in a-SiGe：H solar cells. A relative increase of 19% in the solar cell efficiency was achieved in comparison to the cell without the ZnO films doped with Al （ZnO：Al）.

Influence of substrate temperature on in situ-textured ZnO thin films grown by MOCVD

The influence of substrate temperature on microstructure, electrical and optical properties of in situ- textured zinc oxide （ZnO） films fabricated by metal organic chemical vapor deposition （MOVCD） had been investigated. Results indicated that the substrate tempera- ture played a very important role on preparation of ZnO thin film. With the raising of temperature, firstly ZnO crystals were perpendicular to the substrate, then they were grown inclining toward the substrate, finally ZnO crystals grown in layers but not regular. Consequently, ZnO film surface morphology changed from smooth to a pyramid structure and then disappeared little by little. Moreover, it was also found in this study that ZnO film was characterized with high crystallinity, low resistivity （2.17 x 10 2） and high transmittance （〉 80%）. These results suggested that ZnO thin film is suitable for front electrode of silicon thin film solar cell.

Effect of Al22Si/ZL102 bimetal interface fabricated by extrusion at neareutectic temperature

The Al22Si/ZL102 bimetal was designed and prepared by extrusion at near-eutectic temperature.The properties and fracture behaviors of different surface treatments between oxide film and zinc coating were compared between the Al22 Si and ZL102 bimetal.The average bonding strength of bimetal with intermittent oxide film interface was about 89.3MPa,which is higher than that of the bimetal fabricated by zinc coating method（about 76.3MPa）.During the process of extrusion,the oxidation film was extruded to crush and the metal was extruded through the micro-cracks of the oxidation film,then the two surfaces were joined together.Altogether,the results showed that extrusion at near-eutectic temperature is favorable for achieving a high-quality metallurgical bonded interface.