Advanced coatings through pulsed magnetron sputtering

Pulsed magnetron sputtering (PMS) has become established as the process of choice for the deposition of dielectric materials for many applications. The process is attractive because it offers stable arc free operating conditions during the deposition of, for example, functional films on architectural and automotive glass, or antireflective/antistatic coatings on displays. Recent studies have shown that pulsing the magnetron discharge also leads to hotter and more energetic plasmas in comparison with continuous dc discharges, with increased ion energy fluxes delivered to the substrate. As such, the PMS process offers benefits in the deposition of a wide range of materials. The present paper describes three examples where PMS has led to either significant enhancement in film properties or enhanced process flexibility: in low friction titanium nitride coatings, in Al doped zinc oxide transparent conductive oxide coatings sputtered directly from powder targets and in thin film photovoltaic devices based on copper (indium/gallium) diselenide. These examples demonstrate the versatility of PMS and open up new opportunities for the production of advanced coatings using this technique

Resistivity measurement of ZnO:AI films for solar cell

Aluminium doped Zinc Oxide films were deposited on glass slide by RF magnetron sputtering using a ZnO target mixed with A120J. All the films were growth in room temperature without intentional heating. The resistivity of the ZnO:AI films were measured using van der Pauw method in terms of the preparation conditions such as RF power, working pressure, deposition time, O2 content in sputtering gas and target-substrate distance. Resistivity of the deposited films shows the following behaviours: decreases with the increasing RF power and film thickness while increase with increasing target substrate distance, and O2 content in sputtering gas. Resistivity for films prepared in different working pressure decreases with the Argon pressure but increased after the optimal pressure of 45mTorr

Penerapan ciri-ciri guru berkesan dalam proses pengajaran dan pembelajaran semasa latihan mengajar dalam kalangan Pelajar Sarjana UTHM

Kajian ini bertujuan untuk mengenal pasti sejauh mana penerapan ciri-ciri guru berkesan di kalangan pelajar sarjana Fakulti Pendidikan Teknikal dan Vokasional (FPTV) dari Universiti Tun Hussein Onn Malaysia (UTHM) dalam pengajaran dan pembelajaran dalam kelas semasa menjalani latihan mengajar serta faktor yang paling dominan. Keduanya, kajian ini adalah untuk melihat tahap persepsi pelajar terhadap ciri-ciri guru berkesan pada guru pelatih dan menentukan sama ada terdapat perbezaan dalam memberi persepsi berdasarkan perbezaan jantina. Kajian ini adalah berbentuk kuantitatif. Kajian ini dijalankan di politeknik premier di Malaysia. Data instrumen yang hendak dikaji diperolehi daripada edaran borang soal selidik. Responden adalah terdiri daripada 182 orang pelajar politeknik dimana terdapat pelajar sarjana FPTV yang sedang menjalani latihan mengajar. Seramai lapan orang pensyarah pelatih telah dipilih secara rawak untuk menjadi sampel penilaian oleh responden. Data yang diperolehi akan di analisis dengan menggunakan pendekatan Rasch dan perisian winsteps 3.69.1.11. Nilai pekali Alpha Cronbach untuk kajian ini adalah 0.98. Dapatan kajian mendapati faktor kebolehan pensyarah kaya ilmu pengetahuan merupakan faktor yang paling dominan dengan nilai min logit -0.13. Dapatan kajian menunjukkan tahap persepi pelajar terhadap ciri-ciri guru berkesan dalam kalangan pensyarah pelatih adalah tinggi. Dari segi memberi persepsi terhadap penyarah pelatih berdasarkan ciri-ciri guru berkesan didapati tidak terdapat perbezaan dalam memberi persepsi walaupun berbeza jantina. Pensyarah pelatih dari UTHM telah menerapkan ciri-ciri guru berkesan dalam pengajaran dan pembelajaran semasa latihan mengajar kerana berdasarkan dapatan kajian secara keseluruhannya responden menunjukkan tahap persetujuan yang tinggi (skor min 4.25). Ini menunjukkan bahawa pensyarah pelatih telah mengaplikasikan kemahiran dan pengetahuan dari segi pedagogi, psikologi semasa menjalani latihan mengajar

Enhanced electrical and optical properties of room temperature deposited Aluminium doped Zinc Oxide (AZO) thin films by excimer laser annealing

High quality transparent conductive oxides (TCOs) often require a high thermal budget fabrication process. In this study, Excimer Laser Annealing (ELA) at a wavelength of 248 nm has been explored as a processing mechanism to facilitate low thermal budget fabrication of high quality aluminium doped zinc oxide (AZO) thin films. 180 nm thick AZO films were prepared by radio frequency magnetron sputtering at room temperature on fused silica substrates. The effects of the applied RF power and the sputtering pressure on the outcome of ELA at different laser energy densities and number of pulses have been investigated. AZO films deposited with no intentional heating at 180 W, and at 2 mTorr of 0.2% oxygen in argon were selected as the optimum as-deposited films in this work, with a resistivity of 1×10−3 Ω.cm, and an average visible transmission of 85%. ELA was found to result in noticeably reduced resistivity of 5×10−4 Ω.cm, and enhancing the average visible transmission to 90% when AZO is processed with 5 pulses at 125 mJ/cm2. Therefore, the combination of RF magnetron sputtering and ELA, both low thermal budget and scalable techniques, can provide a viable fabrication route of high quality AZO films for use as transparent electrodes

Nanostructured cobalt manganese ferrite thin films for gas sensor application

Ferrite compounds are very important because of their optical, electrical or magnetic properties. Moreover, many papers relate to their development as possible gas sensor. In this study, we were interested in using cobalt-manganese-ferrite as sensitive layer for CO2 sensor devices. Such an application required a high surface activity, and consequently a small crystallite size and a large surface area. The physical vapor deposition (RF-sputtering) is widely used for thin film synthesis. In this work, porous thin films were obtained from a Co1Mn0.65Fe1 3504 target sputtered under pure argon plasma, by optimizing the deposition parameters (gas pressure, power). The deposition time was adjusted in order to obtain an average thickness of 300 nm. Structural (G-XRD) and microstructural (SEM-FEG, gas adsorption, electron microprobe) analyses were carried out on these thin films. The chemical composition was found to be homogeneous on the whole surface of the samples. The grain size ranged from 10 to 25 nm. The surface enhancement factor (SEF) was about 100 m2/m2, which is equivalent to a specific surface area of 76 m2/g for the ferrite layer. In conclusion, these nanostructured cobalt-manganese-ferrite films appear to be quite suitable for an application as gas sensors

Thin film engineering for transparent thin film transistors

Zinc oxide (ZnO) and Indium Gallium Zinc Oxide (IGZO) thin films are of interest as oxide semiconductors in thin film transistor (TFT) applications, due to visible light transparency, and low deposition temperature. There is particular interest in ZnO and IGZO based transparent TFT devices fabricated at low temperature on low cost flexible substrates. However, thermal annealing processes are typically required to ensure a good performance, suitable long term stability, and to control the point defects which affect the electrical characteristics. Hence there is interest in post deposition processing techniques, particularly where alternatives to high temperature thermal treatments can be utilised in combination with low temperature substrates. This thesis presents the results of a series of experimental studies as an investigation into photonic (excimer laser) processing of low temperature ZnO and IGZO thin films deposited by RF magnetron sputtering and/or by high target utilisation sputtering (HiTUS), to optimise the microstructure and electrical properties for potential use in thin film electronic applications. ZnO thin films were grown at various deposition parameters by varying oxygen flow rates, RF power, oxygen concentration, and growth temperatures

Development of thin film photovoltaic cells based on low cost metal oxides

The major market barriers to the use of photovoltaic solar cells are high cost and long payback time of conventional technologies, based largely on the silicon material. In order to overcome the environmental problem resulting from the consumption of fossil fuels, all western countries are required to impose heavy subsidies to encourage the use of solar cells in the reduction of carbon consumption; thereby making them highly unsustainable. Therefore, it is necessary to develop solar cells based on low-cost metal oxides with large natural resources. The objective of this program is to investigate the effects of doping on the structural, optical and electrical properties of low-cost metal oxides, such as doped ZnO and copper oxides (CuO and Cu4O3). These are synthesised via sputter deposition and thermal oxidation method in air. Al doped ZnO is an n-type direct semiconductor with a band gap of around 3.5eV. Its crystalline structure is wurtzite, which is deposited widely by the RF reactive magnetron sputtering technology. In my work, the Al doped ZnO thin films were deposited by sputter with metal and ceramic targets. On the one hand, the influence of RF power on the structural, electrical and optical properties of Al doped ZnO thin films were investigated when they were deposited with metal targets. Conversely, the influence of O2 flow rate on the structural, electrical and optical properties of Al doped ZnO thin films was examined when they were deposited with ceramic targets. CuO is a p-type indirect semiconductor with a narrow band gap of 1.0-1.4eV. Its crystalline structure is monoclinic crystal system. CuO nanowires (NWs) were fabricated by the thermal oxidation method in air. It was found that CuO NWs not only grows on Cu sheets, but also on the Si, FTO, Al doped ZnO and glass substrates. For the growth of CuO NWs, the expanding parameters should meet the following requirements: growing temperature: >390°C and growing duration: ≥6hrs. The peeling-off of the CuO NWs on Cu sheets resulted from the formation of Cu8O and Cu64O between the Cu sheets and Cu2O layer. The electrical properties of a single CuO NW were measured using a nano probe station. The contact behaviour between a CuO NW and metal electrodes (Au and W) was schottky. The electrical resistivity of a CuO NW depended on the diameter of the NW. The contact behaviour between CuO NWs on Cu sheets with silver paste top electrodes was schottky as well. A simple PV cell based on CuO NWs-PCBM p-n heterojunction was fabricated, and the short circuit current, open voltage and fill factor of the PV cell was also measured. It indicated that CuO NWs can be utilized to fabricate diodes and PV cells. Copper oxides thin films were deposited by RF reactive magnetron sputtering technology. The phase structure of copper oxides thin films depended on the sputtering parameters. When the thin film was deposited without a bias power, only CuO was detected in the copper oxide thin films. The electrical properties of CuO thin films depended on the O2 fraction during the sputter process. The current-voltage (I-V) characteristics of CuO thin films with Cu electrodes demonstrated that it was influenced by the O2 fraction during the sputter process. Moreover, Cu4O3 is a p-type indirect semiconductor with narrow band gap of 1.0-1.4eV and its crystalline structure is tetragonal crystal system. When the copper oxide thin films were deposited with a bias power, only Cu4O3 phase was detected. Its structural, optical and electrical properties were studied. The optical band gap of Cu4O3 thin film was 1.37eV. Hall properties of Cu4O3 thin films were 1020cm-3, 10-2cm2·V-1·s-1 and 10-1Ω·cm. The Cu4O3-Al Abstract III doped ZnO p-n heterojunction demonstrated excellent rectifying performance, indicating that Cu4O3 is a good candidate for fabricating diodes and PV cells. In addition, Cu4O3 thin films were annealed at different temperatures in air. Furthermore, I studied the influence of annealing temperature on the structural, optical and electrical properties of Cu4O3 thin films

Optimisation of amorphous zinc tin oxide thin film transistors by remote-plasma reactive sputtering

The influence of the stoichiometry of amorphous zinc tin oxide (a-ZTO) thin films used as the semiconducting channel in thin film transistors (TFTs) is investigated. A-ZTO has been deposited using remote-plasma reactive sputtering from zinc:tin metal alloy targets with 10%, 33%, and 50% Sn at. %. Optimisations of thin films are performed by varying the oxygen flow, which is used as the reactive gas. The structural, optical, and electrical properties are investigated for the optimised films, which, after a post-deposition annealing at 500 °C in air, are also incorporated as the channel layer in TFTs. The optical band gap of a-ZTO films slightly increases from 3.5 to 3.8 eV with increasing tin content, with an average transmission ∼90% in the visible range. The surface roughness and crystallographic properties of the films are very similar before and after annealing. An a-ZTO TFT produced from the 10% Sn target shows a threshold voltage of 8 V, a switching ratio of 10$^8$, a sub-threshold slope of 0.55 V dec$^{-1}$, and a field effect mobility of 15 cm$^2$ V$^{-1}$ s$^{-1}$, which is a sharp increase from 0.8 cm$^2$ V$^{-1}$ s$^{-1}$ obtained in a reference ZnO TFT. For TFTs produced from the 33% Sn target, the mobility is further increased to 21 cm$^2$ V$^{-1}$ s$^{-1}$, but the sub-threshold slope is slightly deteriorated to 0.65 V dec$^{-1}$. For TFTs produced from the 50% Sn target, the devices can no longer be switched off (i.e., there is no channel depletion). The effect of tin content on the TFT electrical performance is explained in the light of preferential sputtering encountered in reactive sputtering, which resulted in films sputtered from 10% and 33% Sn to be stoichiometrically close to the common Zn$_2$SnO$_4$ and ZnSnO$_3$ phases.Engineering and Physical Sciences Research Council (Grant ID: EP/M013650/1