Microstructures and photovoltaic performances of bismuth-ion doped Cu(In,Ga)Se2 films prepared via sputtering process

Bismuth-ion doped Cu(In,Ga)Se₂ (CIGS) solar cells were fabricated via sputtering technique. The influence of bismuth-ion doping on structural and photovoltaic characteristics of the fabricated CIGS films were explored in details. With doping of bismuth ions, the grain sizes of CIGS layers were enhanced appreciably due to liquid-phase sintering with the yielded intermediate compound. The secondary ion mass spectroscopy profile results indicated that the diffusion of bismuth ions into CIGS layers promoted dissemination of gallium species from the back contacts to the surface of CIGS layers. According to Hall measurement analysis, the carrier concentration in CIGS films was enhanced significantly with the doping of bismuth ions in the prepared films. The conversion efficiency of the bismuth-ion doped samples was increased approximately 10% in comparison with undoped samples due to the elevated gallium-ion diffusion and grain growth. Various photovoltaic parameters including saturated current and diode factors of the prepared doped CIGS solar cells were decreased owing to the inhibition of electron-hole recombination. This investigation demonstrated the improved photovoltaic performance and the structural characteristics of fabricated CIGS films after the doping of bismuth ions.     

CIGS absorbing layers prepared by RF magnetron sputtering from a single quaternary target

Cu(In_1−xGa_x)Se₂ (CIGS) thin films were prepared by RF magnetron sputtering from a single quaternary target at multiple processing parameters. The structural, compositional, and electrical properties of the as-deposited films were systematically investigated by XRD, Raman, SEM, and Hall effects analysis. The results demonstrate that by adjusting the processing parameters, the CIGS thin films with a preferential orientation along the (112) direction which exhibited single chalcopyrite phase were obtained. The films deposited at relatively higher substrate temperature, sputtering power, and Ar pressure exhibited favorable stoichiometric ratio (Cu/(In+Ga):0.8–0.9 and Ga/(In+Ga):0.25–0.36) with grain size of about 1–1.5 µm, and desirable electrical properties with p-type carrier concentration of 10¹⁶−10¹⁷ cm⁻³ and carrier mobility of 10–60 cm²/Vs. The CIGS layers are expected to fabricate high efficiency thin film solar cells.     

Growth and characterization of Cu(In,Ga)Se2 thin films by nanosecond and femtosecond pulsed laser deposition

In this work, CuIn_{1 - x} Ga _x Se₂ (CIGS) thin films were prepared by nanosecond (ns)- and femtosecond (fs)-pulsed laser deposition (PLD) processes. Different film growth mechanisms were discussed in perspective of the laser-produced plasmas and crystal structures. The fs-PLD has successfully improved the inherent flaws, Cu_{2 - x} Se, and air voids ubiquitously observed in ns-PLD-derived CIGS thin films. Moreover, the prominent antireflection and excellent crystalline structures were obtained in the fs-PLD-derived CIGS thin films. The absorption spectra suggest the divergence in energy levels of radiative defects brought by the inhomogeneous distribution of elements in the fs-PLD CIGS, which has also been supported by comparing photoluminescence (PL) spectra of ns- and fs-PLD CIGS thin films at 15 K. Finally, the superior carrier transport properties in fs-PLD CIGS were confirmed by fs pump-probe spectroscopy and four-probe measurements. The present results indicate a promising way for preparing high-quality CIGS thin films via fs-PLD.     

ZAO薄膜使用射频溅射法生长之参数的研究

以氧化铝锌陶瓷为溅射靶材,在氩气环境下,使用射频溅射法在玻璃基片上制备氧化铝锌(ZAO)薄膜。通过调节气体压强、基片温度、溅射功率制膜,得到以C轴(002)为选择取向的氧化锌薄膜。由XRD、原子力显微镜(AFM)等对薄膜进行分析。结果表明,制备薄膜的最佳条件为:溅射压强0.4 Pa,溅射功率200 W,基片温度300℃。     

Characterization of luminescent properties of ZnO:Er thin films prepared by rf magnetron sputtering

ZnO:Er thin films were deposited on c-plane sapphire substrates by rf magnetron sputtering and annealed at 700 °C under air and H₂ atmospheres for the luminescent improvement. The effects of sputtering parameters and the annealing conditions on visible and 1.54 μm IR emissions were investigated. Structural and luminescent properties strongly depended on the deposition conditions and annealing atmospheres. By tuning the excitation wavelength, ZnO:Er thin films exhibited a strong emission band at around 465 nm and a weak emission at 525 nm originated from the energy transition of ⁴I_15/2–⁴F_5/2 and ⁴I_15/2–²H_11/2, respectively, while 1.54 μm IR emissions due to ⁴I_15/2–⁴I_13/2 transition.     

Steady-state and transient room-temperature photoluminescence of AlN films,prepared by RF magnetron sputtering

Near UV (363.8 nm, continuous radiation) and UV (248 nm, pulse radiation) laser excited photoluminescence (PL) has been measured for aluminum nitride films at room temperature. The films were deposited by the radio frequency sputtering of Al target in an argon–nitrogen–hydrogen (Ar:N₂:H₂) gas mixture. The PL peak energies are found to be influenced by deposition conditions such as gas mixture flow rates and substrate temperature. The steady-state PL is analyzed based on the microstructures and electron spectra of the films. The changes in the PL spectra across samples deposited under different conditions have been correlated to the variation in the electron density distribution. Transient PL signal measured after short (20–25 ns) pulse KrF laser excitation reveals a long PL decay lifetime of 160±25 μs.     

Structural and mechanical properties of CNx thin films prepared by magnetron sputtering

In an attempt to define the role of nitrogen in CN chemical bonding and in the formation of CN_x thin films, several coatings with a variable concentration of N₂ were grown onto (100) Si substrates using magnetron sputtering in N₂/Ar discharge. The chemical composition of the as-deposited films was investigated by means of Rutherford backscattering spectroscopy (RBS) and showed an [N]/[C] ratio up to 0.7. Raman and Fourier transform infrared (FTIR) spectroscopy were carried out to measure the optical vibration properties for studying the bonding state of nitrogen.By means of grazing incidence X-ray diffraction (XRD) and transmission electron microscopy (TEM) electron diffraction the structure of the deposited films was proven to be mainly amorphous containing small crystallites of CN_x compounds. Scanning tunneling microscopy (STM) shows the clusterlike surface of the films where the cluster size is characterized by scaling behaviour. The mechanical properties of the CN_x thin films adhering their substrates were investigated using the nanoindentation technique. From the load–displacement curve the hardness H and the Young's modulus E of the films were calculated.The relationships between deposition parameters and properties of CN_x films are shown and discussed. In particular, the influence of the applied r.f. power and the role of the N₂ partial pressure are demonstrated.     

Corrosion performance of thin hydrogenated amorphous carbon films prepared by magnetron sputtering

Hydrogenated amorphous carbon (a-CH_x) films were prepared by magnetron sputtering at different H₂/Ar gas flow ratios. Several sets of perpendicular magnetic recording disks with a-CH_x overcoats of 5 nm were prepared for accelerated environmental corrosion test. The corrosion spots on the disks and the corrosion products were analyzed using optical surface analyzer and time-of-flight secondary ion mass spectroscopy, respectively. Other techniques, such as Raman spectroscopy, atomic force microscopy nano-scratch and contact angle measurement, were used to characterize the properties of a-CH_x films. Compared to pure carbon overcoat, all the a-CHx overcoats have better corrosion resistance and higher polar component of surface free energy. The a-CH_x film with appropriate H content shows the highest scratching resistance, and the corresponding disk has the lowest corrosion area on the disk surface after the accelerated corrosion.     

Effect of Fe-doping on the structural,optical and magnetic properties of ZnO thin films prepared by RF magnetron sputtering

In this paper, we report the fabrication and systematic characterization of Fe Doped ZnO thin Films. Fe_xZn_1−x O (x=0<0.05) films were prepared by RF magnetron sputtering on Si (400) substrate. Influence of Fe doping on structural, optical and magnetic properties has been studied. The X-ray diffraction (XRD) analysis shows that Fe doping has affected the crystalline structure, grain size and strain in the thin films. The best crystalline structure is obtained for 3% Fe Doping as observed from Atomic Force Microscopy (AFM) and X-ray diffraction (XRD). The magnetic properties studied using Vibrating Sample Magnetometer reveals the room temperature ferromagnetic nature of the thin films. However, changing the Fe concentration degrades the magnetic property in turn. The mechanism behind the above results has been discussed minutely in this paper.     

Structural and optical properties of ZnS thin films deposited by RF magnetron sputtering

Zinc sulfide [ZnS] thin films were deposited on glass substrates using radio frequency magnetron sputtering. The substrate temperature was varied in the range of 100°C to 400°C. The structural and optical properties of ZnS thin films were characterized with X-ray diffraction [XRD], field emission scanning electron microscopy [FESEM], energy dispersive analysis of X-rays and UV-visible transmission spectra. The XRD analyses indicate that ZnS films have zinc blende structures with (111) preferential orientation, whereas the diffraction patterns sharpen with the increase in substrate temperatures. The FESEM data also reveal that the films have nano-size grains with a grain size of approximately 69 nm. The films grown at 350°C exhibit a relatively high transmittance of 80% in the visible region, with an energy band gap of 3.79 eV. These results show that ZnS films are suitable for use as the buffer layer of the Cu(In, Ga)Se₂ solar cells.     

Electronic phase transition in CrN thin films grown by reactive RF magnetron sputtering

Chromium nitride thin films were prepared by reactive radio frequency magnetron sputtering on glass and Si(001) substrates. Thin films were grown at different nitrogen to argon flow rate ratio and their effect on the film composition, band gap and electronic phase transition was studied by different experimental technique. X-ray diffraction analyses establish that CrN films predominantly grow in [111]_CrN and [002]_CrN directions irrespective of the substrates used for the growths. The band gap was found to vary with the composition of the films. All films are semiconducting at room temperature and show discontinuity in their resistivity versus temperature curve indicating electronic transition. But the low temperature electronic phase depends on the growth conditions and composition of the films.     

Improved physical properties of Al-doped ZnO thin films deposited by unbalanced RF magnetron sputtering

Room temperature Al-doped ZnO (AZO) thin films with improved crystalline and optical properties were grown on normal glass substrates using unbalanced RF magnetron sputtering technique. To modify the plasma density towards the substrate and enhance the crystalline nature, an additional magnetic field ranging from 0 to 6.0 mT has been applied to the AZO target by proper tuning of solenoid coil current from 0 to 0.2 A respectively, which plays a significant role for controlling the physical properties of AZO films. The results from XRD studies indicate that all AZO films were composed of hexagonal wurtzite structure with better crystal quality through the applied magnetic field, ZnO (002) plane as a preferred growth. Furthermore, XPS studies suggested that symmetric chemical shifts in the binding energies for the Zn 2p and O1s levels with applied magnetic field. SEM analysis revealed the formation of a smooth, homogeneous and dense morphological surface with applied magnetic field. From AFM analysis, it was observed that the applied magnetic field strongly influenced the grain size and the films showed decreasing tendency in electrical resistivity. Films exhibited superior optical transmittance more than 94% in the visible region essentially due to the formation of better crystalline nature. The results indicate that improved band gap from 3.10 to 3.15 eV with additional magnetic field varied from 0 to 6.0 mT respectively.     

Structural,optical and electrical properties of indium doped Cu2ZnSn(S,Se)4 thin films synthesized by the DC and RF reactive magnetron cosputtering

Element doping into the Cu₂ZnSn(S,Se)₄ (CZTSSe) absorber is an effective method to optimize the performance of thin film solar cells. In this study, the Cu₂In_xZn_1-xSn(S,Se)₄ (CIZTSSe) precursor film was deposited by magnetron cosputtering technique using indium (In) and quaternary Cu₂ZnSnS₄ (CZTS) as targets. Meanwhile, the In content was controlled using the direct current (DC) power on In target (P_In). A single kesterite CIZTSSe alloy was formed by successfully doping a small number of In³⁺ into the main lattice of CZTSSe. The partial Zn²⁺ cations were substituted by In³⁺ ions, resulting in improving properties of CZTSSe films. Morphological analysis showed that large grain CIZTSSe films could be obtained by doping In. The well-distributed, smooth, and dense film was obtained when the P_In was 30 W. The band gap of CIZTSSe could be continuously adjusted from 1.27 to 1.05 eV as P_In increased from 0 to 40 W. In addition, the CIZTSSe alloy thin film at P_In = 30 W exhibited the best p-type conductivity with Hall mobility of 6.87 cm²V^?1s^?1, which is a potential material as the absorption layer of high-performance solar cells.     

Electrochemical synthesis of ba- and Sr-based titanate thin films using Ti electrode prepared by RF sputtering

Barium and strontium titanate films were electrochemically synthesized onto Ti thin film prepared by RF sputtering. Applied current waveform was modulated to investigate the film growth mechanism. Superimposed cathodic pulses accelerated the formation of titanate thin films, and both the electrode surface pH and (Ba²⁺, Sr²⁺) ion size had a strong influence on film formation. Titanate film formation mechanism was investigated with a scanning electron microscope, an X-ray diffractometer and an electrochemical quartz crystal microbalance (EQCM).Insitu mass change of Ti electrode during electrolysis indicated that electrochemical method sets a limit to film growth.     

Fabrication of CaLa4(Zr0.05Ti0.95)4O15 thin films by RF magnetron sputtering

Crystalline CaLa₄(Zr_0.05Ti_0.95)₄O₁₅ thin films deposited on n-type Si substrates byRF magnetron sputtering at a fixed RF power of 100 W, an Ar/O₂ ratio of 100/0, an operating pressure of 3 mTorr, and different substrate temperatures were investigated. The surface structural and morphological characteristics analyzed by X-ray diffraction and atomic force microscopy were sensitive to the deposition conditions, such as the substrate temperature. The diffraction pattern showed that the deposited films had a polycrystalline microstructure. As the substrate temperature increased, the quality of the CaLa₄(Zr_0.05Ti_0.95)₄O₁₅ thin films improved, and the kinetic energies of the sputtered atoms increased, resulting in a structural improvement of the deposited CaLa₄(Zr_0.05Ti_0.95)₄O₁₅ thin films. A high dielectric constant of 16.7 (f=1 MHz), a dissipation factor of 0.19 (f=1 MHz), and a low leakage current density of 3.18×10⁻⁷ A/cm² at an electrical field of 50 kV/cm were obtained for the prepared films.     

Influence of postdeposition annealing on the properties of ZnO films prepared by RF magnetron sputtering

ZnO films were prepared on unheated silicon substrate by RF magnetron sputtering technique. Postdeposition annealing of ZnO films in vacuum were found to improve film structure and electrical characteristics, such as dense structure, smooth surface, stress relief and increasing resistivity. Suitable annealing temperature also reduced loss factor. The correlation between annealing conditions and the physical structure of the films (crystalline structure and microstructure) was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The preferred annealing condition has been found to improve ZnO film characteristics for piezoelectric applications. An over-mode acoustic resonator using the ZnO film after annealing at 400 °C in vacuum circumstance for 1 h showed a large return loss of 42 dB at the center frequency of 1.957 GHz.     

Fast preparation of Cu(In,Ga)Se2 and CuIn(S,Se)2 bulk materials by combustion synthesis

CuIn_1‐xGa_xSe₂ and CuIn(S_ySe_1‐y)₂ bulk materials with relative densities of 93.4%‐96.2% have been prepared by combustion synthesis, from elementary reactants and in a reaction time of a few seconds. The samples have a chalcopyrite lattice structure, and the lattice parameters decrease with increasing x and y. The substitution of In with Ga and Se with S in CuInSe₂ causes an increase in the bandgap. In combustion synthesis, the high temperature accelerates the reaction and results in fast densification, the high heating rate simplifies the reaction path and avoids the formation of intermediate compounds, and the gas pressure depresses the evaporation of reactants. As a fast, furnace‐free, and scalable technique, combustion synthesis may offer a low‐cost way to produce CuInSe₂‐based materials and bring new possibilities to their commercial applications.     

Characterization of non-stoichiometric Ga2O3-x thin films grown by radio-frequency powder sputtering

We report the synthesis and characterization of non-stoichiometric Ga₂O_3-x thin films deposited on sapphire (0001) substrates by radio-frequency powder sputtering. The chemical and electronic states of the non-stoichiometric Ga₂O_3-x thin films were investigated. By sputtering in an Ar atmosphere, the as-grown thin films become non-stoichiometric Ga₂O_2.7, due to the difference in sputtering yield between Ga and O species of the Ga₂O₃ target. The electronic states of the thin films consist of ~85% Ga³⁺ and ~15% Ga¹⁺, corresponding to Ga₂O₃ and Ga₂O, respectively. The films have the electrical characteristics of a semiconductor, with electrical conductivity of approximately 5.0 × 10^-4 S cm^-1 and a carrier concentration of 4.5 × 10¹⁴ cm^-3 at 300 K.     

直流溅射ITO薄膜光电性能研究

采用直流溅射法制备了高性能的ITO薄膜。结果表明,氧气分压比和衬底温度对薄膜的方阻、可见光透射率具有重要的影响。其最佳值分别为0.5/50和350℃;同时,随着膜厚的增加,薄膜的晶粒增大,导电率也相应降低。     

Field modulation in Na-incorporated Cu(In,Ga)Se2 (CIGS) polycrystalline films influenced by alloy-hardening and pair-annihilation probabilities

The influence of Na on Cu(In,Ga)Se2 (CIGS) solar cells was investigated. A gradient profile of the Na in the CIGS absorber layer can induce an electric field modulation and significantly strengthen the back surface field effect. This field modulation originates from a grain growth model introduced by a combination of alloy-hardening and pair-annihilation probabilities, wherein the Cu supply and Na diffusion together screen the driving force of the grain boundary motion (GBM) by alloy hardening, which indicates a specific GBM pinning by Cu and Na. The pair annihilation between the ubiquitously evolving GBMs has a coincident probability with the alloy-hardening event.PACS: 88. 40. H-, 81. 10. Aj, 81. 40. Cd.