Zn Thin Films Research Articles

PREPARATION OF CZTS THIN FILM EMPLOYING RAPID THERMAL PROCESSING METHOD

CZTS thin film was fabricated by sulfurization process of deposited thin films on Mo coated glass substrates. Cu, Zn, and Sn thin film layers were deposited sequentially to form Glass/Mo/CuSn/Zn/Cu. The CuSn layer in the stacked structure was formed by annealing process in the sputtering chamber after sequential deposition of Cu and Sn, respectively. The sulfurization process was performed by rapid thermal processing method (RTP) so as to obtain kesterite CZTS structure. The obtained CZTS thin film was analyzed using several characterization methods such as EDX, XRD, Raman spectroscopy, SEM and PL measurements. The EDX measurements showed that elemental loss was not observed after the annealing process in sulfur atmosphere. The fabricated CZTS thin film showed Cu stoichiometric and Zn rich composition. The XRD pattern of annealed sample revealed formation of kesterite CZTS structure. The Raman spectra of the sample proved formation of kesterite CZTS structure. In addition, some CTS phases were detected in the structure by Raman spectroscopy. Polycrystalline surface microstructure was seen in SEM surface measurement. The room temperature PL measurement exhibited a transition around at 1.39 eV that is very close to band gap of kesterite CZTS structure. Overall, with this study, it has been shown that the CZTS thin film structure can be easily produced using the RTP method with very high heating rate.

Positive corona streamer interaction with metalized dielectric: Possible mechanism of cathode destruction

This paper examines the effect of pulsed positive point-to-plane corona discharge in millimeter air gaps on the surface of a metalized dielectric. A footprint method was applied to reveal the streamer–surface interaction with Al and Zn thin films (20–50 nm) as a sensitive indicator. A thin metal film-dielectric substrate system was destructed at relatively low typical average currents of 20–50 μA during exposure times of 2–200 s. Destruction occurred in local zones with a size of several μm2 per one discharge pulse, which is substantially lower than the conventional streamer size of several tens of micrometers. An offered model of electro-thermal heating of the cathode layer shows that the dielectric surface temperature can achieve 1000 K and more during the single current pulse of submicrosecond duration. The indicated mechanism is possibly responsible for the effects of the discharge plasma interaction with low heat conductivity cathodes, including biological objects. Intensive heating of the cathode layer should be considered when modeling the streamer–cathode interaction.

Electrical properties of zinc nitride and zinc tin nitride semiconductor thin films toward photovoltaic applications

Abstract Zn3N2 (ZN) and ZnSnN2 (ZTN) are a promising class of nitride semiconductors for photovoltaic and light-emitting-diode applications due to their particular electrical and optical properties, elemental abundance and non-toxicity. So far, most of the experimental results show the degenerate carrier concentration. However, we find that low-temperature growth of these films in a chamber with ultra-high background vacuum can attain a non-degenerate electrical conductivity. This work provides the recent progress of the electrical properties of ZN and ZTN semiconductor thin films. The origins for the high carrier concentrations in ZN and ZTN have been discussed, demonstrating that non-intentional oxygen and hydrogen-related defects play significant roles in such high carrier concentrations. The strategies to suppress the carrier concentrations have also been addressed, such as ultra-high vacuum conditions and low temperature growth.

Atomic Layer Deposition of Intermetallic Fe4Zn9 Thin Films from Diethyl Zinc.

We present a new type of atomic layer deposition (ALD) process for intermetallic thin films, where diethyl zinc (DEZ) serves as a coreactant. In our proof-of-concept study, FeCl3 is used as the second precursor. The FeCl3 + DEZ process yields in situ crystalline Fe4Zn9 thin films, where the elemental purity and Fe/Zn ratio are confirmed by time-of-flight elastic recoil detection analysis (TOF-ERDA), Rutherford backscattering spectrometry (RBS), atomic absorption spectroscopy (AAS), and energy-dispersive X-ray spectroscopy (EDX) analyses. The film thickness is precisely controlled by the number of precursor supply cycles, as expected for an ALD process. The reaction mechanism is addressed by computational density functional theory (DFT) modeling. We moreover carry out preliminary tests with CuCl2 and Ni(thd)2 in combination with DEZ to confirm that these processes yield Cu–Zn and Ni–Zn thin films with DEZ as well. Thus, we envision an opening of a new ALD approach based on DEZ for intermetallic/metal alloy thin films.

Fabrication and investigation of TiO1.5/ZnO nanocomposite nanosensor for detection of CO and CH4 gases

In this study, a Zn thin film was deposited on a quartz substrate by DC magnetron sputtering. ZnO nanoparticles were then synthesized by thermal oxidation of this thin film in the air at 700°C for 1 h. Afterward, structural properties of nanostructured ZnO films were studied through XRD spectroscopy, FESEM, EDX and AFM images. Results indicated that the prepared nanosized ZnO particles, which have a porous form with a wurtzite structure, are uniformly distributed on the surface and that the features of porosity and uniformity can greatly improve the sensing properties of ZnO sensors. Then, a thin film of Ti was deposited on ZnO by DC magnetron sputtering, and, subsequently, 100 nm of Au electrodes were used to cover it by evaporation method. Finally, the sample was sintered in airflow at 150°C for 1 h, and the TiO1.5 nanoparticles were formed from sputtered Ti thin film in the uncovered area between Au contacts. Prepared sensors were tested at 300°C of substrate for different concentrations of CH4 and CO gases. Experiments indicated that compared to similar ZnO sensors, the sensitivity of the TiO1.5/ZnO nanosensor to CH4 and CO gases significantly improved, whereas it is not influenced by H2 gas. These data suggest that gas detection by TiO1.5/ZnO nanocomposite, produced by optimizing the manufacturing conditions, can detect minuscule traces of CH4 and CO gases with very high sensitivity and stability as well as better response (Rgas/Rair) in comparison with previous ZnO-based sensors.

The Effect of Sputtering Time and Substrate Type on the Structure of Zinc Nanoparticles Prepared by the DC Sputtering Technique

Zn thin films have been successfully deposited on two different substrates, FTO and p-type Si (111), with thickness (112, 186) nm at (1 and 8) min, respectively, via DC sputtering technique in this work. Structural properties of the prepared thin films were studied using X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM). XRD results showed that the samples have a hexagonal wurtzite structure. From the results of FESEM images, all the samples showed a uniform distribution of granular surface shape morphology. The grain sizes of the Zn thin films were estimated based on measured X-ray diffraction patterns. Zn thin film thicknesses were increased as the sputtering time increased for all substrates. The best result was the deposition of zinc nanoparticles on Si (p-type) at 1 min, where the particle size was at the peak of 7 nm.

Effect of Zn(S,O,OH) Buffer Thin Films Formed on CIGS through Different Stages and Reaction Processes in Chemical Bath Deposition: Interpretations from Mechanisms and Transformation Kinetics Perspective

Herein, Zn(S,O,OH) is used as a buffer material for Cu(In,Ga)Se2 (CIGS) solar cells instead of CdS to increase the quantum efficiency and remove toxicity. To control the fine thickness of the Zn(S,O,OH) thin films in the chemical bath deposition (CBD) method, a quartz crystal microbalance (QCM) system is introduced by measuring the frequency change. As the frequency changes are adjusted according to the S/O ratio of the Zn(S,O,OH) buffer (Zn buffer) produced during the reaction, the formed phase and thickness are cross‐validated several times to obtain the accurate thickness. These different S/O ratios can be modified by different deposition mechanisms and reaction processes depending on the reaction rate of material formation. Therefore, to investigate the associated mechanism and reaction process in detail, Zn buffer thin films are formed and characterized using two different Zn sources (zinc sulfate and zinc acetate) that affect the reaction rate due to the anion effect. In addition, the optimal deposition range is obtained by comparing the performances of the solar cells with Zn thin films of the same thickness, deposited through different stages in a continuous CBD reaction. Finally, the effect of Zn buffers using different Zn sources on the interfaces with CIGS is investigated in the band alignment.

Zn-Doped Iron Oxide Thin Films Prepared by Spray Pyrolysis Technique and Characterized for Use as an Efficient Photocatalyst for Methyl Green Organic Dye

Ultrasonic Spray Pyrolysis (USP) technique was used to prepare undoped and (2, 4, 6 and 10 at. %) Zn-doped iron oxide (FexOy:Zn) thin films for use in photocatalytic applications. The effect of Zn ion substitution on structural, optical, and electrical properties was studied. The X-ray diffraction patterns showed that there are two different phases of iron oxide, a hematite phase (α‑Fe2O3) and a magnetite phase (Fe3O4) that crystallized in the prepared samples. The nominal fractions of α‑Fe2O3 and Fe3O4 phases changed from 74 % to 42 % for the hematite phase and from 26 % to 58 % for the magnetite phase and this confirmed that the Zn doping favored the growth of Fe3O4 phase. The crystallite size decreased from 15.43 nm to 8.99 nm, while the micro-strain changed from 0.0056 to 0.0215 and the dislocation density from 0.0099 nm‑2 to 0.0639 nm‑2. The unit cell parameters were also improved when the doping rate was changed. Optical measurements showed that the energy gap decreased from 2.26 eV to 2.16 eV, the film thickness changed from 569 nm to 479 nm while the refractive index increased from 2.99 to 3.51 and the Urbach energy from 544 meV to 558 meV. Electrical measurements performed by the two-point probe method showed that the electrical conductivity increased directly with increasing Zn concentration reaching 18.5 10‑15 (Ω.cm)‑1 with 10 at. % Zn concentration. The variation of the electrical conductivity curves versus the sample heating temperature as well as the activation energy showed a semiconductor behavior of the films. Zinc doped iron oxide thin films exhibit 51.85 % photocatalytic degradation efficiency for methyl green organic dye.

Enhancement in optoelectronic properties of lanthanum co-doped CdO: Zn thin films for TCO applications

This work reports on structural, electrical, optical, and photosensing properties of La and Zn co-doped CdO thin films . The co-doped CdO thin films were prepared on glass substrates using the nebulizer spray method at 350 °C. From the structural analysis, a decrease in the crystallite size from 20 to 16 nm is observed against the incorporation of La in CdO:Zn. Inclusion of La in CdO:Zn has also changed the surface morphology with a reduction in the roughness of the thin film samples. EDX analysis confirmed the incorporation of La with CdO: Zn in the prepared films. The bandgap value of the prepared samples increased with the increase in La concentration. A 1.5 wt% of La co-doped with CdO:Zn thin film sample produces low resistivity of 6.81 × 10 -4 Ω cm and a better figure of merit of 8.4 × 10 −4 Ω -1 . Finally, the fabricated photodetector with 1.5 wt% of La co-doped with CdO:Zn thin film shows a higher photocurrent and an ideality factor value of 3.4 . The photosensing properties of the fabricated (p-Si/CdO–Zn–La (1.5%)) photodetector shows a higher responsivity (R) value of 1.18 AW -1 , specific detectivity (D*) value of 4.90 × 10 9 Jones, and external quantum efficiency (EQE) value of 274% with 3.0 mW/cm 2 light intensity . The switching characteristics of the photodetector show a faster rise time (2.9s) and fall time (3.6s) suggesting the fabricated device suitable for photosensing applications. • Doping of La in CdO:Zn has changed the surface morphology with a reduction in the roughness of the samples. • A 1.5 wt% of La co-doped CdO:Zn sample produces low resistivity of 0.68 Ωcm and a better figure of merit of 8.4 × 10 −4 Ω -1 . • Fabricated p-Si/CdO–Zn–La (1.5%)) photodetector shows a higher responsivity (R) value of 1.18 AW -1 , specific detectivity (D*) value of 4.90 × 10 9 Jones, and external quantum efficiency (EQE) value of 274%. • The switching characteristics of the photodetector show a faster rise time (2.9s) and fall time (3.6s).

Improved optoelectronic properties of Yttrium co-doped CdO:Zn thin films fabricated by nebulizer spray pyrolysis method for TCO applications

To understand the effect of Yttrium (Y) co-doping with CdO:Zn towards optoelectronics applications, the thin films were coated by the nebulizer spray pyrolysis route. The microstructural studies (XRD) reveals that the crystallite size decreases from 20 to 15 nm with the increase of Y concentrations. The surface topography of the films has been strongly influenced by the Y doping which is evident from the AFM images. The presence of Cd, O, Zn, and Y has been confirmed through the EDX spectrum. The transparency is higher (81%) for the CdO:Zn-Y(1.5%) film. The decreasing trend in the values of the optical dielectric constant is observed with increases in yttrium content. The enhancement in the carrier concentration (12 × 1020cm−3) and reduction in the electrical resistivity (8.4 × 10−4Ωcm) have been observed for the CdO:Zn-Y(1.5%) film via the Hall-effect measurements. In addition, the heterojunction p-Si/n-CdO:Zn-Y(1.5%) photodiode was fabricated to understand the optical sensing properties. The current values of the fabricated photodiode are found to enhance as the intensity of the illumination increases from1.0 to 3.0 mW cm−2. Moreover, the photodiode exhibits the highest responsivity, detectivity, and external quantum efficiency value of 1.45 AW−1, 6 × 109 Jones, and 339%, respectively with excellent switching speeds. This work provided a guideline to develop a TCO layer and photodiode towards the applications of optoelectronic-based devices.

Tape-based novel ZnO nanoaggregates photodetector

Flexible photonic devices are of great importance for bio-integrated optoelectronic systems and wearable sensors. Here we describe the design and experimental procedure of highly sensitive photodetector based on ZnO nanoaggregates grown onto heat-resistant flexible adhesive tape. Zn thin film has been oxidized onto the heat-resistant tape using a horizontal furnace under water vapor flow. The obtained results reveal well-defined nanoaggregates ZnO with superior structural and optical properties. The prepared films show a strong and sharp diffraction peak along the (002) plane suggesting a well-crystallized ZnO phase. Besides, ZnO nanoaggregates exhibit distinct light transmission/absorption characteristics for UV light. Photoresponse characterizations indicate that the fabricated device possesses outstanding properties. At low applied voltages, the device demonstrates a significant difference between dark and light currents. A photosensitivity of 83.45 × 102 to 365 nm light pulses was achieved with high stability and reversibility. The study revealed that the fabricated photodetector could be a very promising candidate for highly sensitive wearable electronic devices.

Fabrication of Dye-Sensitized Solar Cells (DSSC) Using Mg-Doped ZnO as Photoanode and Extract of Rose Myrtle (Rhodomyrtus tomentosa) as Natural Dye

A dye-sensitized solar cell (DSSC) device using Mg-doped Zn thin films as photoanode and fruit extract of rose myrtle (Rhodomyrtus tomentosa) as the natural dye was investigated. The effect of annealing temperature (400-550°C) on the films of photoanode was systematically studied using an X-ray diffractometer (XRD), UV-Visible Near Infrared (UV-Vis NIR) Spectrophotometer, scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). XRD confirm that all sample has the wurtzite hexagonal with crystallite size of 25 nm. The SEM images reveal particles on the surface of the Mg-doped ZnO thin film of irregular shapes. Increasing the annealing temperature leads to a larger particle size and slightly increases bandgap energy. The dye sensitizer of extracted rose myrtle (Rhodomyrtus tomentosa) has a strong absorption at the visible light region. The maximum efficiency of the DSSC device is 3.53% with Mg-ZnO photoanode annealed at 500°C.

Optical and structural properties of vacuum annealed multilayer nanostructured CdZnS thin films deposited by thermal evaporation

The CdS and multilayers of CdS and Zn thin films were deposited on glass substrates by thermal evaporation. Subsequently, deposited films were annealed under a high vacuum to diffuse Zn into CdS films. Vacuum annealed films of CdS and CdZnS (CZS) were characterized for structural, surface morphology and optical properties. The XRD results showed that films were polycrystalline with hexagonal and cubic structures having predominant diffraction corresponding to the (0 0 2) plane. It was also observed that the lattice constants decreased, grain size and bandgap increased as Zn content increases in deposited films. The transmittance of as-deposited films increased drastically by vacuum annealing up to 90% in visible and NIR regions. EDX results confirmed that the concentration of Zn increased with the increase of Zn layer thickness into the multilayer structure of CZS films. The results obtained suggest that the blue shift of the absorption edge of CZS films will be useful for enhancing the efficiency of photovoltaic cells and optoelectronic devices in this region. The results reported in this paper revealed that the refractive index, optical band gap and lattice constants of CZS films can be tailored by the variation of Zn concentration. The potential of vacuum annealing is also elaborated to diffuse metallic Zn into CdS films.

Influence of Zinc Doping on the Structural, Morphological, Optical and Electrical Properties of Copper Oxide Thin Films Prepared by Jet-Nebulizer Spray Pyrolysis Technique

This research details the deposition and characterization of adding zinc (Zn) impurities with different doping concentrations (1%, 3%, and 5%) into copper oxide (CuO:Zn) by using a jet nebulizer spray pyrolysis system. The impact of zinc doping on the different copper oxide properties was investigated. The structural studies confirm that pure copper oxide and zinc doped copper oxide thin films are matched with monoclinic structure. High resolution schottky field emission scanning electron microscopy and Energy dispersive spectrum analysis identifies the surface structure and chemical composition of pure CuO and CuO: Zn thin films. EDS spectra reveal the occupancy of Cu, O, and Zn elements in the pure CuO and CuO:Zn thin films. The highest transmittance was observed as 66.91% for 5% Zn concentration. The absorption studies clearly indicated that the absorbance of the films was decreased when Zn doping concentration increase. The energy band gap value (Eg) is calculated as 2.01eV for pure CuO and the value of Eg for CuO:Zn thin films are varied from 2.07 to 2.26 eV. Keithley high resistance and low current electrometer was used to measure direct current conductivity of both pure CuO and CuO: Zn thin films and maximum conductivity value was observed for CuO: Zn (5%) thin film.

Band Structure and Thermoelectric Properties of Ni<sub>(x)</sub>Zn<sub>(1-x)</sub>Fe<sub>2</sub>O<sub>4</sub>

Thermoelectric materials has made a great potential in sustainable energy industries, which enable the energy conversion from heat to electricity. The band structure and thermoelectric properties of Ni(x)Zn(1-x)Fe2O4 have been investigated. The bulk pellets were prepared from analytical grade ZnO, NiO and Fe2O3 powder using solid-state method. It was possible to obtain high thermoelectric properties of Ni(x)Zn(1-x)Fe2O4 by controlling the ratios of dopants and the sintering temperature. XRD analysis showed that the fabricated samples have a single phase formation of cubic spinel structure. The thermoelectric properties of Ni(x)Zn(1-x)Fe2O4 pellets improved with increasing Ni. The electrical conductivity of Ni(x)Zn(1-x)Fe2O4 pellets decreased with increasing Ni content. The electrical conductivity of Ni(x)Zn(1-x)Fe2O4 (x = 0.0) is (0.515 x10-3 Scm-1). The band structure shows that ZnxCu1-xFe2O4 is an indirect band gap material with the valence band maximum (VBM) at M and conduction band minimum (CBM) at A. The band gap of Ni(x)Zn(1-x)Fe2O4 increased with increasing Ni content. The increasing band gap correlated with the lower electrical conductivity. The thermal conductivity of Ni(x)Zn(1-x)Fe2O4 pellets decreased with increasing Ni content. The presence of Ni served to decrease thermal conductivity by 8 Wm-1K-1 over pure samples. The magnitude of the Seebeck coefficient for Ni(x)Zn(1-x)Fe2O4 pellets increased with increasing amounts of Ni. The figure of merit for Ni(x)Zn(1-x)Fe2O4 pellets and thin films was improved by increasing Ni due to its high Seebeck coefficient and low thermal conductivity.

INVESTIGATION OF STRUCTURAL, MORPHOLOGY AND SELF-CLEANING PROPERTIES OF GO:AG, GO:SI AND GO:ZN NANO-COMPOSITES THIN FILMS SYNTHESIZED BY SPRAY PYROLYSIS TECHNIQUE

A wide variety of approaches have been explored by researchers in the attempt to attain a system with controllable wetting properties. The hydrophilic surfaces can be used in anti-fogging applications, biomedical, filtration, heat pipes, and many others. hydrophilic surface has strong affinity to water whereas hydrophobic surface repel water. In this research, the synthesis of graphene oxide- silver, graphene oxide- silica and graphene oxide-zinc nano-composite were done by spray pyrolysis method in order to investigate their self-cleaning properties. The nano-composite thin films were characterized by X-ray diffraction (XRD), field-emission transmission electron microscope (FE-SEM) . The xrd results confirm the formation of desired thin films. Atomic force microscope (AFM) was used to calculate the thickness and RMS value of thin films. RMS values for GO, GO:Ag, GO:Si and GO:Zn thin films were 17.57, 185.78, 125.64, 37.23 nm, respectively. According to the results of contact angle and AFM images, GO:Zn thin film has the lowest roughness and therefore the lowest contact angle and a relatively good hydrophilic surface.

Eutectic Structure of Sn–Zn Thin Films Formed during Electrodeposition

Eutectic Structure of Sn–Zn Thin Films Formed during Electrodeposition

(Invited) Developing the Electrodeposition of High Energy Density Anodes for 3D Architectures for Rechargeable Batteries

As Li-ion batteries continue to improve in all metrics, new markets are now opening to portable energy. However, the fundamental challenges are still the same: how do we improve how much energy a particular material can store, how quickly it can charge and discharge safely, while enabling effective communication between all components of a particular cell? It is not sufficient to simply discover and improve new materials, we have to also consider the development of efficient, manufacturable architectures that enable the best performance for a particular material.We are working to incorporate high surface area structures of novel anode materials into a 3D interdigitated solid-state battery architecture. The significant advantage to this architecture is that the diffusion length for Li+between the cathode and anode will be dramatically reduced, which should lead to much faster charging rates. The structure and composition of the anode is critical to the energy density, power density, cycle life, and safety of the overall battery. I will discuss electrodeposited M-Sb (where M = Ni, Cu, Zn) thin films and high surface area structures that have been investigated as alloy anodes for Li-ion batteries to elucidate the effects of both the film composition and substrate interactions on cycling stability and lifetime. The results discussed will demonstrate that important composition and substrate factors for anode cycling performance are being developed that are likely applicable to other systems. A key theme in this work is how to develop materials architectures that not only have attractive properties for the chosen application (energy storage), but that are also ideally suited to elucidating and understanding degradation mechanisms for high energy density materials. I will also discuss my opinions on the need for integrating a big-picture view of manufacturability for applied materials research, as well as the challenges and opportunities in moving research and development from an academic lab into the marketplace.

Effect of doping on microstructure and optical properties of ternary structure of Zn1−x−yBxCyO (B=Cu, C=Co) nano thin films

We report the results of an in depth study of optical and microstuctural properties of thin films of Zn1−x−yCuxCoyO system (x = 0,00 and 0.02, y = 0.00, 0.01, 0.02, 0.03, 0.04. and 0.05) which are grown by the sol–gel method. We have performed differential thermal analysis, and thermo gravimetric analysis/difference thermogravimetric analysis, x-ray diffraction, scanning electron microscopy, energy dispersive spectrometer, atomic force microscopy and UV–VIS spectrophotometer experiments. We have found that all of the studied samples are in hexagonal wurtzite structure and oriented along the (002) direction with a very weak signal for the (101) reflection. We have also found that the lattice parameter c increases with doping. All the films showed wrinkle network structure with nano-sized crystals and the grain size was observed to decrease with increasing Co doping. The bandgap was found to decrease from 3.28 to 3.22 eV with doping. All the above results will be discussed in detail.

Double-Sided Heat-Exchange CBD System for Homogeneous Zn(O,S) Thin Films in Highly Efficient CIGS Solar Devices

Zn(O,S) thin film as one of the most promising alternative buffer layers in Cu(In,Ga)Se2 solar devices has drawn considerable attention and been intensively studied in recent years. However, the re...