A Novel Semiconductor CIGS Photovoltaic Material and Thin-Film ED Technology

In order to achieve low cost high efficiency thin film solar cells,a novel Semiconductor Photovoltaic (PV) active material CuIn 1-x Ga x Se 2 (CIGS) and thin film Electro Deposition (ED) technology is explored.Firstly,the PV materials and technologies is investigated,then the detailed experimental processes of CIGS/Mo/glass structure by using the novel ED technology and the results are reported.These results shows that high quality CIGS polycrystalline thin films can be obtained by the ED method,in which the polycrystalline CIGS is definitely identified by the (112),(204,220) characteristic peaks of the tetragonal structure,the continuous CIGS thin film layers with particle average size of about 2μm of length and around 1 6μm of thickness.The thickness and solar grade quality of CIGS thin films can be produced with good repeatability.Discussion and analysis on the ED technique,CIGS energy band and sodium (Na) impurity properties,were also performed.The alloy CIGS exhibits not only increasing band gap with increasing x ,but also a change in material properties that is relevant to the device operation.The beneficial impurity Na originating from the low cost soda lime glass substrate becomes one prerequisite for high quality CIGS films.These novel material and technology are very useful for low cost high efficiency thin film solar cells and other devices.     

Oxide-based thin film transistors for flexible electronics

The continuous progress in thin film materials and devices has greatly promoted the development in the field of flexible electronics.As one of the most common thin film devices,thin film transistors (TFTs) are significant building blocks for flexible platforms.Flexible oxide-based TFTs are well compatible with flexible electronic systems due to low process temperature,high carrier mobility,and good uniformity.The present article is a review of the recent progress and major trends in the field of flexible oxide-based thin film transistors.First,an introduction of flexible electronics and flexible oxide-based thin film transistors is given.Next,we introduce oxide semiconductor materials and various flexible oxide-based TFTs classified by substrate materials including polymer plastics,paper sheets,metal foils,and flexible thin glass.Afterwards,applications of flexible oxide-based TFTs including bendable sensors,memories,circuits,and displays are presented.Finally,we give conclusions and a prospect for possible development trends.     

氧化鑭薄膜閘極結構與電性並應用在砷化鎵高速場效應電晶體研製

This paper investigates the feasibility of using a lanthanum oxide thin film （La2O3） with a high dielectric constant as a gate dielectric on GaAs pHEMTs to reduce gate leakage current and improve the gate to drain breakdown voltage relative to the conventional GaAs pHEMT. An E/D mode pHEMT in a single chip was realized by selecting the appropriate La2O3 thickness. The thin La2O3 film was characterized： its chemical composition and crystalline structure were determined by X-ray photoelectron spectroscopy and X-ray diffraction, respectively. La2O3 exhibited good thermal stability after post-deposition annealing at 200, 400 and 600℃ because of its high binding-energy （835.6 eV）. Experimental results clearly demonstrated that the La2O3 thin film was thermally stable. The DC and RF characteristics of Pt/La2O3/Ti/Au gate and conventional Pt/Ti/Au gate pHEMTs were examined. The measurements indicated that the transistor with the Pt/La2O3/Ti/Au gate had a higher breakdown voltage and lower gate leakage current. Accordingly, the La2O3 thin film is a potential high-k material for use as a gate dielectric to improve electrical performance and the thermal effect in high-power applications.     

Review of recent progresses on flexible oxide semiconductor thin film transistors based on atomic layer deposition processes

The current article is a review of recent progress and major trends in the field of flexible oxide thin film transistors (TFTs),fabricating with atomic layer deposition (ALD) processes.The ALD process offers accurate controlling of film thickness and composition as well as ability of achieving excellent uniformity over large areas at relatively low temperatures.First,an introduction is provided on what is the definition of ALD,the difference among other vacuum deposition techniques,and the brief key factors of ALD on flexible devices.Second,considering functional layers in flexible oxide TFT,the ALD process on polymer substrates may improve device performances such as mobility and stability,adopting as buffer layers over the polymer substrate,gate insulators,and active layers.Third,this review consists of the evaluation methods of flexible oxide TFTs under various mechanic al stress conditions.The bending radius and repetition cycles are mostly considering for conventional flexible devices.It summarizes how the device has been degraded/changed under various stress types (directions).The last part of this review suggests a potential of each ALD film,including the releasing stress,the optimization of TFT structure,and the enhancement of device performance.Thus,the functional ALD layers in flexible oxide TFTs offer great possibilities regarding anti-mechanical stress films,along with flexible display and information storage application fields.     

The effect of the film thickness and doping content of SnO2:F thin films prepared by the ultrasonic spray method

This paper reports on the effects of film thickness and doping content on the optical and electrical properties of fluorine-doped tin oxide. Tin(II) chloride dehydrate, ammonium fluoride dehydrate, ethanol and HCl were used as the starting materials, dopant source, solvent and stabilizer, respectively. The doped films were deposited on a glass substrate at different concentrations varying between 0 and 5 wt% using an ultrasonic spray technique. The SnO2 :F thin films were deposited at a 350 C pending time(5, 15, 60 and 90 s). The average transmission was about 80%, and the films were thus transparent in the visible region. The optical energy gap of the doped films with 2.5 wt% F was found to increase from 3.47 to 3.89 eV with increasing film thickness, and increased after doping at 5 wt%. The decrease in the Urbach energy of the SnO2:F thin films indicated a decrease in the defects. The increase in the electrical conductivity of the films reached maximum values of 278.9 and 281.9( cm)1for 2.5 and 5 wt% F, respectively, indicating that the films exhibited an n-type semiconducting nature. A systematic study on the influence of film thickness and doping content on the properties of SnO2:F thin films deposited by ultrasonic spray was reported.     

Influence of Cu_xS back contact on CdTe thin film solar cells

We present a detailed study on CuxS polycrystalline thin films prepared by chemical bath method and utilized as back contact material for CdTe solar cells.The characteristics of the films deposited on Si-substrate are studied by XRD.The results show that as-deposited CuxS thin film is in an amorphous phase while after annealing,samples are in polycrystalline phases with increasing temperature.The thickness of CuxS thin films has great impact on the performance of CdS/CdTe solar cells.When the thickness of the film is about 75 nm the performance of CdS/CdTe thin film solar cells is found to be the best.The energy conversion efficiency can be higher than 12.19%,the filling factor is higher than 68.82% and the open-circuit voltage is more than 820 mV.     

Magnetic interference gonioapparent thin film based on metal-dielectric-metal structure for optical security devices

In recent years, magnetic interference thin films have gained wide attention in optical security devices field by virtue of their gonioapparent and dynamic 3D effects. Based on the color mechanism of metal-dielectric Fabry-Perot structure, a novel seven-layer magnetic thin film structure is proposed by adopting the ultrathin metal layer as a bonding layer and a pure metallic Ni layer as a magnetic layer as well as a reflective layer. Color target optimization optimac method is utilized that realizes the seven-layer metal-dielectric optically variable magnetic thin film structure with green at the normal incidence and purple-red at 60°. The structure effectively solves the delaminate problem and simplifies the multilayer structure. Through different combined magnetic field designs, the magnetic orientation experiment of the prepared magnetic optically variable thin film is carried out, and the 3 D anti-counterfeiting with remarkable dynamic color change effect is obtained, which provides a new solution for optical security devices.     

A non-polarization short-wave-pass thin film edge filter

Multilayer dielectric thin film edge filter has serious polarization sensitivity under oblique incidence. The cutoff-bands of the s-polarization and p-polarization light in conventional edge filter will separate obviously under 45° oblique inci- dence, which limits its application. Based on the two chosen materials TiO2 and SiO2, a novel stack structure is pro- posed to design the non-polarization short-wave-pass thin film edge filter. By using the （4H 4L 4H） as the matching layers, the polarization separation at 3 dB transmittance for the thin film edge filter cutoff-band is less than 1 nm at the incident angle of 45°. In this way, the non-polarization short-wave-pass edge filter is easily designed and fabricated.     

Poly-Si Thin Film Grown by Excimer Laser Crystallization and Its Ellipsometric Analysis

A novel approach of two-step laser crystallization for the growth of poly-Si thin film on glass substrate is investigated. Using this approach, we fabricated poly-Si thin film transistors with electron mobility of 103 cm2/V·s and on/off current ratio of 1×10~7.They are better than those of the poly-Si TFTs fabricated by conventional single-step excimer laser crystallization. We also analyzed the structure of the laser crystallized poly-Si thin film by spectroscopic ellipsometry, and proposed the models to simulate the poly-Si thin film and calculated the ellipsometric spectra. The calculated results are in good agreement with the measured results.     

Study on Manganin High Pressure Array Sensor

A new kind of thin film manganin aray gauge is fabricated by adopting a new sensorfabrication technique.The sensitive materials (manganin thin films) are first deposited by magnetronsputtering on fused silica substrates,and then covered by a layer of SiO_2 thin films by electron beamevaporation.Based on impedance match method of "back configuration",the highest pressure measuredin Al target is 51.68 Gpa,the highest pressure in SiO_2 package is 35.396 Gpa and the piezoresistancecoefficient k is 0.026 Gpa~(-1).The upper limit and measure precision of sensor is improved.     

Microcrystalline Structure and Luminescence of ZnS Thin Films

The electroluminescence thin films doped with erbium, fabricated by thermal evaporation with two boats, are analyzed by X-ray diffraction(XRD).The relationship between electroluminescence brightness and microstructure of the thin films is obtained.The results reveal that the large grain size in high index plane of deposited microcrystalline film has an effect on electroluminescence characteristics of the film devices.     

TiO2 Thin Film UV Detectors Deposited by DC Reactive Magnetron Sputtering

CrystallineTiO2 thin films were prepared by DC reactive magnetron sputtering on indium--tin oxide(ITO) thin film deposited on quartz substrate, the photoconductive UV detector on TiO2 thin films was based on a sandwich structure of C/TiOz/ITO. The measurement of the I—V characteristics for these devices shows good ohmic contact. The photoresponse of TiO2 thin films was analyzed at different bias voltage. The detector shows a good photoresponse with a rise time of 2 s and a fall time of 40 s, the photocurrent is linearly increased with the bias voltage.     

Investigation of AlN Thin Films as Buried Insulator in SOI Structure

Self-heating effects in silicon-on-insulator (SOI) devices limit the applicability of SOI materials in electronics in cases where high power dissipation is expected. AlN film as a potential candidate for buried insulator material in SOI-structures is investigated. Ion-beam-enhanced deposition (IBED) is used to manufacture large area AlN films. SIMS measurements indicate the formation of AlN films. The characterization of the films reveals that the quality of the films strongly depends on the evaporation rate of Al. For the film with high quality deposited at 0.05nm/s, it has higher component of N, excellent dielectric property and a smoother surface with roughness RMS value of 0.13nm, and can be bonded directly at room temperature by the smart-cut process. SOI structure with the AlN film as buried insulator has formed successfully for the first time, which is confirmed by XTEM micrograph.     

The effect of thin film structure and properties on gold ball bonding

The gold ball bonding process is widely used for making interconnections between integrated circuit chips and package lead frames, yet the relationships between the wire/substrate materials properties and the bond formation processes are not yet well understood. While the creation of a metallurgical bond at the interface between the wire and substrate is required, the deformation of the wire and substrate also play an important role in bond formation. Bonding to thin film substrates is of particular interest, since thin films often exhibit mechanical behavior distinctly different from bulk materials. In the present study, a systematic investigation has been conducted to understand the effects of the structure and properties of aluminum thin films on the quality of gold ball bonds. A series of aluminum thin films was fabricated with systematic variations in hardness, roughness, thickness, and composition. Gold wires were ball bonded to these substrates, and the bondability and bond shear strengths were assessed. Metallographic sections of several of these specimens were made and examined in the scanning electron microscope. The results show that the film thickness has the most dominant effect on the bondability and bond strength; films that were 0.5 μm thick often exhibited low strength or poor bondability. Very hard films also gave poor results. Ultimately, these results can be used to predict the wire bond reliability expected from various types of thin film metallization.     

Tris（8—Hydroxyquinoline）Aluminum／2—（4—Biphenylyl）—5—（4—Tertbutylphenyl）—1,3,3—O—xadiazole Organic Multiple Quantum Wells for Electroluminescent Devices

Organic multiple quantum wells(OMQWs) consisting of alternating layers of organic materials have been fabricated from tris(8-hdroxyquinoline) aluminum(Alq)and 2-(4-biphenylyl)-5-(4-tertbutylphenyl)-1,3,3-oxadiazole(PBD)by a multisource-type high-vacuum organic molecular deposition.From the small-angle X-ray diffraction patterns of Alq/PBD OMQWs,a periodically layered structure is confirmed through the entire stack.The Alq layer thickness in the OMQWs was varied from 1 nm to 4 nm.From the optical aborption, photoluminescence and electroluminescence measurements,it is found that the exciton energy shifts to higher energy with decreasing Alq layer thickness,The changes of the exciton energy could be interpreted as the confinement effects of exciton in the Alq thin layers.Narrowing of the emission spectrum has also been observed for the electroluminescent devices(ELDs)with the OMQWs structure at room temperature.     

Substrates and interlayer coupling effects on Mo1-xWxSe2 alloys

Two-dimensional(2D) transition metal dichalcogenides alloys are potential materials in the application of photodetectors over a wide spectral range due to their composition-dependent bandgaps. The study of bandgap engineering is important for the application of 2D materials in devices. Here, we grow the Mo1-xWxSe2 alloys on mica, sapphire and SiO2/Si substrates by chemical vapor deposition(CVD) method. Mo1-x Wx Se2 alloys are grown on the mica substrates by CVD method for the first time. Photoluminescence(PL) spectroscopy is used to investigate the effects of substrates and interlayer coupling force on the optical bandgaps of as-grown Mo1-xWxSe2 alloys. We find that the substrates used in this work have an ignorable effect on the optical bandgaps of as-grown Mo1-xWxSe2. The interlayer coupling effect on the optical bandgaps of as-grown Mo1-xWxSe2 is larger than the substrates effect. These findings provide a new way for the future study of the growth and physical properties of 2D alloy materials.     

Preparation of 3 Inch Double-Sided YBa2Cu3O7-X High Temperature Superconducting Thin Films

Owing to its excellent electrical property, YBCO thin film is much better than metal in the application for microwave devices. It makes the devices smaller,lighter, and with higher quality factor and lower insertion loss. YBCO thin film has attracted attentions for many years. Aiming at the uniformity and property of 3-inch double-sided YBCO thin film, the following aspects is considered in this dissertation:     

Preparation of 3 Inch Double-Sided YBa2Cu3O7-X High Temperature Superconducting Thin Films

Owing to its excellent electrical property,YBCO thin film is much better than metal in the application for microwave devices. It makes the devices smaller, lighter, and with higher quality factor and lower insertion loss. YBCO thin film has attracted attentions for many years. Aiming at the uniformity and property of 3-inch double-sided YBCO thin film, the following aspects is considered in this dissertation:     

Synthesis,properties, and applications of large-scale two-dimensional materials by polymer-assisted deposition

Two-dimensional(2D) materials have attracted considerable attention because of their novel and tunable electronic,optical, ferromagnetic, and chemical properties. Compared to mechanical exfoliation and chemical vapor deposition, polymer-assisted deposition(PAD) is more suitable for mass production of 2D materials owing to its good reproducibility and reliability. In this review, we summarize the recent development of PAD on syntheses of 2D materials. First, we introduce principles and processing steps of PAD. Second, 2D materials, including graphene, MoS2, and MoS2/glassy-graphene heterostructures, are presented to illustrate the power of PAD and provide readers with the opportunity to assess the method. Last, we discuss the future prospects and challenges in this research field. This review provides a novel technique for preparing 2D layered materials and may inspire new applications of 2D layered materials.