OPRACOWANIE TECHNOLOGII OSADZANIA I POMIARÓW ZMIĘNNOPRĄDOWYCH ULTRACIENKICH WARSTW MIEDZI

In this paper, the transport properties of discontinuous 4 nm copper layers obtained by dual-source non-reactive magnetron sputtering in the presence of argon are presented. The value of resistance and capacitance of the current parallel to the plane of these layers can be adjusted independently by changing the nominal thickness of the metallization. The influence of frequency on the conductivity of the obtained structures in the range from 4 Hz to 8 MHz was studied. Additionally, in order to compare the non-oxidized and oxidized layers, some of them were heated at 500 °C. Based on the results obtained, the mechanism of electric charge transfer was determined, the knowledge of which is essential for planning further experiments based on this sputtering method and potential selection of future application of the structures. Statistical measurements at room temperature will serve as a reference for the conductivity and resistivity values obtained by mathematical calculations from measurements of resistance, capacitance, phase shift angle, and dielectric loss tangent as a function of temperature from 20 K to 375 K, which are expected in further studies on the obtained structures. The work is an introduction to the technology of obtaining multi-layer metal-dielectric structures.W niniejszej pracy przedstawione zostały właściwości transportowe nieciągłych 4 nm warstw miedzi otrzymanych metodą dwuźródłowego niereaktywnego rozpylania magnetronowego w obecności argonu. Wartość rezystancji i pojemności prądu równoległego do płaszczyzny tych warstw można dostrajać niezależnie poprzez zmianę nominalnej grubości metalizacji. Przebadano wpływ częstotliwości na konduktywność otrzymanych struktur w zakresie od 4 Hz do 8 MHz. Dodatkowo, w celu porównania nieutlenionych i utlenionych warstw niektóre z nich zostały wygrzane w temperaturze 500 °C. Na podstawie otrzymanych wyników określono mechanizm przenoszenia ładunków elektrycznych, którego znajomość jest niezbędna do planowania kolejnych eksperymentów bazujących na tej metodzie napylania oraz potencjalnym doborze przyszłego zastosowania struktur. Statystyczne pomiary w temperaturze pokojowej posłużą za punkt odniesienia dla wartości konduktywności i rezystywności otrzymanych na drodze obliczeń matematycznych z pomiarów rezystancji, pojemności, kąta przesunięcia fazowego oraz tangensa strat dielektrycznych w funkcji temperatury od 20 K do 375 K, które przewidywane są w dalszej części badań nad otrzymanymi strukturami. Praca stanowi wstęp do technologii otrzymywania wielowarstwowych struktur typu metal-dielektryk

Effect of Implantation Time of Cupper Nitride onto ITO Thin Films: Structural, Morphological, Electrical, and Optical Properties

Copper nitride (Cu3N) thin films have been implanted onto an electron beam evaporated films of indium tin oxide (ITO) from Cu metal target using reactive dc Magnetron Sputtering (dcMS) technique in a nitrogen/argon atmosphere at room temperature. The implantation parameter was kept constant excepting the implantation time. The effect of implantation time upon microstructural, morphological, electrical, and optical properties have been studied. The elemental composition of the as-deposited and Cu3N implanted has been studied by using the EDXS technique, and the spectrum shows peaks belonging to In, Sn, O, Cu, and N. A zinc blend structure was observed for all the investigated films with no sign of impurities. The optical direct energy bandgap E_g^opt is found to decreases from 3.49 eV to 2.62 eV with increasing the implantation time of Cu3N. The refractive index n is increased with increasing the exposure time of implantation. The refractive index has abnormal behavior in the infrared region due to the strong absorption in this region that appears in transmission spectra. The electrical resistivity decreases from 1908.22 .cm to 165.24 .cm with increasing the duration time of implantation

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

Deposition and characterization of niobium films for SRF cavity application

Niobium coated copper cavities are an interesting alternative to bulk niobium ones for Superconducting Radio Frequency (SRF) applications to particle accelerators. The magnetron sputtering is the technology developed at CERN for depositing niobium Alms and applied over the past twenty years. Unfortunately, the observed degradation of the quality factor with increasing cavity voltage, not completely understood, prevents the use of this technology in future large accelerators designed to work at gradients higher than 30 MWm, with quality factors of the order of 1010 (or higher). At the beginning of the new millennium some new deposition techniques have been proposed to overcome the difficulties encountered with the sputtering technique. This paper compares the properties of niobium films obtained with the magnetron sputtering and with a cathodic arc deposition in ultra-high vacuum (UHVCA). The UHVCA-produced Nb Alms have structural and transport properties closer to the bulk ones, providing a promising alternative for niobium coated, highvoltage and high-Q copper RF cavities, with respect to the standard magnetron sputtering technique. Preliminary results and possible approaches to whole cavity UHVCA coating will be presented and discussed

p-Type conducting transparent characteristics of delafossite Mg-doped CuCrO2thin films prepared by RF-sputtering

The growth of technologically relevant compounds, Mg-doped CuCrO2 delafossite thin films, on a quartz substrate by radio-frequency sputtering is reported in this work. The deposition, performed at room temperature, leads to a nanocrystalline phase with extremely low roughness and high density. Delafossite characteristic diffraction peaks were obtained as a function of the thermal treatment under primary vacuum. The electrical conductivity was optimized until 1.6 S cm−1 with an optical transmittance of 63% in the visible range by a 600 °C annealing treatment under primary vacuum applied for 4 h. The transport properties were analyzed by Seebeck and Hall measurement, integrated spectrophotometry and optical simulation. These measurements highlighted degenerated semiconductor behavior using a hopping mechanism with a high hole concentration (1021 cm−3) and a low mobility (0.2 cm2 V−1 s−1). The direct optical bandgap of 3.3 eV has been measured according to Tauc's relationship. A refractive index of 2.3 at a wavelength of 1100 nm has been determined by spectroscopic ellipsometry and confirmed by two independent modellings of the optical transmittance and reflectance spectra. All these p-type TCO optoelectronic characteristics have led to the highest Haacke's figure of merit (1.5 × 10−7 Ω−1) reported so far for such delafossite material

Fabrication of Nb\u3csub\u3e3\u3c/sub\u3eSn by Magnetron Sputtering for Superconducting Radiofrequency Application

Particle accelerators are considered as an important device that has wide applications in cancer treatment, sterilizing waste, preserving foods, ion implantation in semiconductor industry, and in production of isotopes for medical applications. Superconducting radiofrequency (SRF) cavities are the building blocks of a linear particle accelerator. Current particle accelerators use niobium (Nb) superconductors as the sheet material to fabricate a single SRF cavity for particle acceleration. With better superconducting properties (critical temperature Tc ~ 18.3 K, superheating field Hsh~ 400 mT), Nb3Sn is considered a potential candidate in SRF technology. Magnetron sputtering is a promising deposition method to fabricate Nb3Sn thin films inside SRF cavities. Superconducting Nb3Sn films were fabricated on Nb and sapphire substrates by magnetron sputtering from a single stoichiometric Nb3Sn target, by multilayer sputtering of Nb and Sn followed by annealing, and by co-sputtering of Nb and Sn followed by annealing. The variation of morphological and superconducting properties was investigated for different substrate temperatures, annealing temperatures, annealing durations, and thicknesses. The film properties were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and energy dispersive X-ray spectroscopy (EDS). The films had crystalline Nb3Sn structure without any presence of poor superconducting Nb6Sn5 and NbSn2 phases. The highest Tc of the films fabricated from the stoichiometric target, multilayer sputtering and co-sputtering were 17.44, 17.93, and 17.66 K respectively. Finally, a cylindrical sputter coater with two identical magnetrons was designed and commissioned to fabricate Nb3Sn films inside a 2.6 GHz SRF cavity. The magnetrons were installed facing opposite to each other in a custom designed vacuum chamber and multilayers of Nb and Sn films on 1 cm2 Nb substrates replicating the beam tubes and equator locations of the cavity and the coated multilayered films were annealed at 950 °C for 3 h. The XRD of the as deposited and annealed films confirmed the formation of Nb3Sn after the annealing. The dissertation discusses the fabrication process, characterized results of the fabricated films, the design of the cylindrical sputter coater and the preliminary data obtained from the sputter coater

Characterization of GaN thin films grown by RF Magnetron Sputtering for fabrication of an AlGaN/GaN HEMT biosensor

Radio-Frequency (RF) Magnetron Sputtering has been used to grow GaN thin films for future fabrication of an AlGaN/GaN HEMT biosensor. A GaN target was sputtered at various parameters on silicon and sapphire substrates, at room temperature and at elevated temperature using substrate heating and post deposition annealing treatment. The research conducted investigates the effects of sputtering gas (Argon or Nitrogen gas), RF power (40W or 50W), and pressure (4mT – 30mT) on the structural properties of the thin films. Imaging tools such as the Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDS), X-ray Diffractometer (XRD), and X-ray photoelectron spectroscopy (XPS) are used for characterization of each thin film. Results revealed that polycrystalline GaN thin film with a hexagonal GaN wurtzite structure can be grown on silicon and sapphire wafers. In addition, oxygen impurities incorporated during the deposition are shown to be reduced by using temperature depositions

Investigation of doped cuprous halides for photovoltaic and display applications

The thesis mainly focuses on the growth and optoelectronic characterisation of the doped cuprous halides (CuX) with high UV/blue emission properties and the light harvesting in the CuBr/Si based heterojunction photovoltaic (PV) cells. Since cuprous halides are short wavelength emitters with high excitonic binding energies, growth of lower resistivity, highly luminescent p and n-type films are essential for the development of the future excitonic based light emitting devices with these materials. We describe the deposition and characterisation of the Zn doped n-type CuCl and oxygen doped p-type CuBr with higher carrier concentration using pulsed dc magnetron sputtering and thermal evaporation followed by oxygen plasma exposure, respectively. The structural and morphological properties of the n-type Zn doped CuCl films are investigated using XRD, SEM and AFM measurements. Our findings show that, the crystallinity of CuCl increases with doping of Zn and the maximum is obtained for the 3 % doped film, beyond which crystallinity decreases. The Zn doping has no deleterious impact on the structural and luminescent properties of CuCl up to a doping percentage of 5. An order of magnitude reduction in the resistivity of the CuCl films is obtained as a result of Zn doping. The resistivity, n-type carrier concentration and carrier mobility corresponding to the 3 % Zn doped films were, respectively 6 Ωcm, ~ 9.8×1018 cm-3 and 0.1 cm2V-1s-1. The influence of Zn doping on the electronic structure of CuCl is investigated using photoemission spectroscopic studies. Our studies on the Cu and Cl core level spectra show the presence of trace amounts of Cu2+ species in the undoped CuCl sample along with the major Cu+ species. This is verified by the observation of the satellite and shoulder peaks in the Cu 2p core level and a higher binding energy tail in the Cl 2p core level spectra. The disappearance of the cupric species with doping of Zn (3 %) is also observed. Furthermore, the shifting of the valence band towards the higher binding energy confirms the filling of the conduction band owing to the Zn doping, which explains the improvement of the conductivity of the doped films. vii We have successfully deposited p-type CuBr films by doping of oxygen. Our findings show that, there is no significant influence on the structural properties of the CuBr up to an oxygen plasma exposure time of 5 min. The investigation of the optical properties confirms good luminescence of the CuBr films up to a plasma exposure time of 3 min. The electrical characterisations of the oxygen plasma exposed films reveal that, oxygen act as a good acceptor for CuBr. The resistivity of the 3 min oxygen plasma exposed samples reduces to the order of ~ 1 Ωcm. SIMS analysis shows that, the diffusion of oxygen is quite good in the CuBr films. The realization of the heterojunction PV cell based on p-CuBr/n-Si is investigated. The I-V characteristics confirm the rectification behaviour of the p-n diode with a turn on voltage of ~ 1 V. The photoresponse properties of the heterojunction are studied by measuring the I-V characteristics under illumination. The photogenerated carrier formation is confirmed by the increased reverse current under illumination of the heterojunction. The wavelength dependence of the photo current was also studied using LED illumination. Development of ultrathin transparent Cr contacts, useful for the electroluminescent device fabrication was also discussed. This can be used as an alternative to well-known Indium Tin Oxide films for the future fabrication of the CuX-based display devices