ICMCTF2009 Session CP: Symposium C Poster Session

Thursday, April 30, 2009 5:00 PM in Room Town & Country
Thursday Afternoon

Time Period ThP Sessions | Topic C Sessions | Time Periods | Topics | ICMCTF2009 Schedule

CP-1 Preparation of TiO2 Photoelectrode by Spray Pyrolysis Technique for the Photovoltaic Application
M.F. Hossain, S. Biswas, M. Shahjahan, T. Takahashi (University of Toyama, Japan)
Among the new generation photovoltaic cell, dye-sensitized solar cells (DSCs) have been the subject of intense study on account of their high conversion efficiency and low cost. Significant progress regarding the efficiency of DSSC devices was made possible by employing nano-porous crystalline TiO2. Among the various deposition techniques, spray pyrolysis technique has also proved to be a simple and inexpensive method particularly useful for large area applications. In the technique, different processing parameters can be varied to control structure and morphology of the thin film. In this present work, porous TiO2 thin films were fabricated. by using spray pyrolysis technique. The solution containing titanium (IV) isopropoxide as a titanium source, acetone and ethanol was sprayed onto SnO2 :F coated glass at different substrate temperatures of 300-500 C.For the fabrication of solar cell, cis-dithiocyanato-bis(2,2’-bipyridyl-4,4’-dicarboxylate) rut henium(II) dye was used along with carbon paste electrodes on SnO2:F coated glass as a counter electrode. All the TiO2 photoelectrodes were characterized by XRD, Raman and UV-visible spectroscopy. Surface morphology of the sample was studied with FE-SEM and AFM. Incident photon-to-current efficiency (IPCE)　was also calculated for all the DSCs with different TiO2electrodes. The amount of dye incorporation was found to be highly dependent on the microstructure and the thickness of the film, as apparent from optical measurements. The variation of IPCE and photoelectric conversion efficiency with solar cells of different TiO2 films is discussed with the analysis of different microstructure of the TiO2 thin films.
CP-2 Effects of Oxygen Flow Ratios and Annealing Temperatures on Raman and Photoluminescence of Titanium Oxide Thin Films Deposited by Reactive Magnetron Sputtering
C.K. Chung, M.W. Liao, C.W. Lai (National Cheng Kung University, Taiwan)
Titanium oxide thin films were deposited on the Si (100) substrate by dc reactive magnetron sputtering at 3-15 % oxygen flow ratios (O2/(Ar+O2)) at room temperature, and then annealed by rapid thermal annealing (RTA) at 350, 550, and 750°C for 2 min in atmosphere. The bonding and luminescence behavior of as-deposited and annealed titanium oxide thin films were analyzed by Raman and photoluminescence (PL) spectroscopy, respectively. Raman spectra results indicate that titanium oxide peaks are weak in the as-deposited films but the pronounced peaks of the mixed anatase and rutile phases were detected after RTA at 350-750°C. The Raman intensity of rutile phase increases with increasing oxygen flow ratio together with annealing temperature. The PL spectra of post-annealed titanium oxide films show a wide FWHM peak in wavelengths of 365- 550 nm. The peak can be fitted into three Gaussian peak at ~380 nm (3.26 eV), ~410 nm (3.02 eV), and ~440nm (2.81 eV). The peak positio n at ~380 nm corresponds to energy bandgap of the anatase phase through electron-hole pair recombination while that at ~410 nm is emitted from the rutile phase. The peak around 440 nm is attributed to oxygen defects. The intensity ratio of the rutile peak to anatase peak increases with increasing oxygen flow ratio. It is in consistent with Raman results. In addition, the relationship between the PL shift of oxygen defects peak and oxygen flow ratio is discussed.
CP-3 Transparent Thermally Stable Poly(etherimide) Film as Flexible Substrate for OLEDs
C. Legnani, W.G. Quirino (CeDO - Inmetro, Brazil); M. Cremona (PUC-Rio, Brazil); V.L. Calil (CeDO - Inmetro, Brazil); G.F. Moreira, C.A. Achete, C. Vilani (Dimat - Inmetro, Brazil)

Due to their applications in many different areas and the simplicity of manufacturing, Organic Light Emitting Diodes (OLEDs) hold great promise in research dedicated to the development of new optoelectronic and photonic devices. These organic devices, mainly small molecule vacuum-deposited ones, can also be fabricated onto plastic film substrates, as for example the polyethylene terephthalate (PET) and the poly carbonate (PC), for the development of flexible OLEDs (FOLEDs). Polyimides are well known for their excellent thermal and chemical stability and good mechanical, optical and electrical properties1. Their strength and heat and chemical resistance are so great that these materials often replace glass and metals, such as steel, in many demanding industrial applications. In this work, a Poly(ether imide) film, PEI, was used as flexible substrate for the fabrication of FOLEDs. The degradation temperature for this material, as reported in the literature, is about 526°C allowing its application in hostile environments. The polymeric film used in this work was obtained by inversion phase by evaporation solvent in nitrogen atmosphere or in vacuum at 80°C, forming a ~0,5 mm thick film. The DSC analyses confirmed the high, 252°C, transition glass temperature (Tg) of this substrate. The optical transmittance is about 86% at 550 nm. In order to achieve the necessary conductive properties indium tin oxide (ITO) thin films were deposited onto PEI at room temperature using a r.f. magnetron sputtering with an r.f. power of 40W, at pressure of 2,5 mPa in Ar atmosphere with a subsequent thermal treatment at 250°C. Resistivity, mobility and carrier concentration of as-deposited ITO films were 3.96x10-4 Ohm-cm, 19.5 cm2/V.s and 8.0x1020/cm3, respectively, and the properties of the post annealed at 250°C were 3.28x10-4 Ohm-cm, 25.6 cm2/V.s and 9.9x1020/c m3, respectively. The mobility and the carrier concentration increase, leading to a decrease in the sheet resistance value. The low resistivity and high stability of the new substrate open the possibilities to develop devices that work in extreme conditions.

1Bor-Kuan Chen, J-U Du, and C-W Hou, IEEE Transactions on Dielectrics and Electrical Insulation 15 (2008) 127.
CP-4 Holographic Grating Formation in PVB Doped Polymer Dispersed Lilquid Crystal Based on PUA
E.H. Kim, Y.G. Jung, U. Paik (Changwon national University, Korea)
Holographic polymer dispersed liquid crystals (HPDLCs) are a relatively new class of materials that have potential device applications in displays and optical shutters. Polymer matrix used in HPDLCs should have high transmittance, adhesive, compatibility with LC, mechanical property and thermal stability to enhance stability of LC droplet and durability as well as electro-optical performance of HPDLC films. In present study, we incorporated different contents of polyvinyl butyral (PVB) into the conventional polyurethane acrylate (PUA) system at a specific composition. PUA ologomer, PVB and LC having simular solubility parameters shows clearly homogeous mixture before photpolymerizaion until the content of PVB is up to 10 wt%, resuling in high diffraction efficiency and good phase separation. As the content of PVB is increased, the hardness, elastic modulus and thermal stability are improved due to the expansion of distant of crosslinks and entanglement by PVB molecular with a high molecular weight relatively compared to PUA oligomer. Off-state diffraction efficiency is increased gradually with increasing PVB content owing to the increase of elasticity of polymer matrix, which implies that phase separation between polymer and LC are augmented. However, the increase of viscosity by adding PVB causes the deterioration of diffraction efficiency, showing lower diffraction efficiency at PVB content of 10 wt% than 1 wt%. Also, HPDLC films having low driving voltage (<50 V), fast response time (<6 ms) and high diffraction efficiency (>70 %) could be fabricated with 1 wt% PVB at 40 wt% LC.
CP-5 Study of Structural and Optical Properties of TiO2:Tb Coatings Prepared by High Energy Reactive Magnetron Sputtering
D. Kaczmarek, J. Domaradzki (Wroclaw University of Technology, Poland); Z.J. Radzimski (Silicon Quest International)
From a review of the literature published during last decade a growing pursuit of obtaining dense crystal structure of different coatings with novel properties may be noticed. Specifically, many papers address titanium dioxide (TiO2) thin film prepared by using different deposition methods. Because of industrial applications, the most important in this field seems to be vapor physical deposition methods, such as magnetron sputtering. Typically, enhanced energy per molecule, which is needed for obtaining a dense structure in the sputtering process, could be assured by appropriate selection of pressure, substrate temperature, argon/oxygen ratio and power of plasma discharge. This work is focused on structural and optical properties of TiO2 thin films doped with terbium. The thin films have been prepared by high energy reactive magnetron sputtering. The method was modified to achieve dense nanocrystalline high temperature stable rutile form of the TiO2 fi lm. Thin films were deposited from a mosaic Ti-Tb target sputtered under oxygen plasma (without argon) at a pressure <10-1 Pa. Besides using only O2 as a reactive and working gas and a low pressure, enhanced energy of particles during the film growth was maintained by increasing the target temperature and by using 164 kHz unipolar pulses with peak amplitude of 1800 V for powering the magnetron source. Using X-ray diffraction, X-ray photoelectron spectroscopy and atomic force microscopy it has been shown that by doping with Tb at a specified amount of 0.4 %, thin films had dense anatase structure. Moreover, this phase was stable even after additional annealing up to 1000 K. Optical properties were studied by the application of optical transmission and photoluminescence measurements (PL). The thin films were transparent in a wide range of optical spectra. The most intense PL spectra were recorded for coatings with the Tb amount of 2.6% where the Tb3+ were embedded into TiO2 – rutile matrix. The energy transfer from TiO2 nanocrystallites to Tb ions that occurred in the thin films was also discussed.
CP-6 The Carbon Effects on the Phase Transformation of Visible-Light Responsive Carbon Containing TiO2 Nanoparticles
Y.-H. Cai, S.-J. Cai (National Dong Hwa University, Taiwan); V. Yeh, S.-B. Wu (Natioanl Dong Hwa University, Taiwan); C.-L. Cheng (National Dong Hwa University, Taiwan)

Visible-light-responsive titanium dioxide (TiO2) has attracted increasing attention recently. While commercially available TiO2 responses only in the UV region, visible-light-responsive TiO2 allows using the visible region of the solar light for photocatalytic reactions. A new carbon containing visible-light-responsive mixed-phase TiO2 has been proposed and proved to be efficient1. Enhanced photocatalytic effects were found when anatase mixed with carbon covered rutile phases in the TiO2 nanoparticles2. In this study, we discuss the phase transformation mechanism on the mixed-phase TiO2 using in-situ Raman mapping and temperature programmed desorption (TPD) methods. The mixed phase was found due to carbon facilitated anatase/amorphous to rutile phase transformation at lower temperature. Evidence on the carbon facilitated anatase/amorphous to rutile phase transformation at lower temperature (200 °C) was demonstrated throu gh in-situ observation of Raman mapping on the transformation. In a further effort to understand the phase transformation, pure anatase phase TiO2 with carbon admixture was employed to study the phase transformation. While the pure anatase phase transformed to ruitle phase at temperature high than 800 °C, the amorphous TiO2 will phase transform facilitated by the carbon inclusion at relatively lower temperature. A possible oxygen deficiency mechanism leading to the phase transformation will be discussed as evidenced from the TPD observation.

1S. Treschev, P. - W. Chou, Y. - H. Tseng, J. - B. Wang, E. Perevedentseva, C. - L. Cheng, Photoactivities of the mixed phase visible-light-activated carbon-containing titanium dioxide: The effect of carbon incorporation, Applied Catalysis B-Environmental, 79, 8-16 (2008).

2P. - W. Chou, S. Treschev, P. - H. Chung, C. - L. Cheng , Y. - H. Tseng, Y. - J. Chen, M. S. Wong, Observation of carbon-containing nanostructured mixed titania phases for visible light photocatalysts, Applied Physics Letters, 89, 131919(2006).
CP-7 Characteristics of Indium Zinc Tin Oxide Thin Film Prepared on Flexible Substrates Using the Hetero-Target Sputtering System
D.H. Kim, Y.S. Rim, H.-W. Choi, K.-H. Kim (Kyungwon University, Korea)
The Indium Zinc Tin Oxide (IZTO) thin films for transparent thin film transistor (TTFT) were deposited on polycarbonate (PC) and polyethersulfone (PES) and glass substrates at room temperature by facing targets sputtering (FTS). Two different kinds of targets were installed on FTS system. One is ITO (In2O3 90wt.%, SnO2 10wt.%), the other is IZO(In2O3 90wt.%, ZnO 10wt.%). As-deposited IZTO thin films were investigated by a UV/VIS spectrometer, an X-ray diffractometer (XRD), an atomic force microscope (AFM) and a Hall Effect measurement system. As a result, we could prepare the IZTO thin films with the resistivity of under 10-4 [Ω•cm] and IZTO thin films deposited on glass substrate showed an average transmittance over 80% in visible range (400~800 nm) in all IZTO thin films except in IZTO thin film deposited at O2 gas flow rate of 0.1 [sccm].
CP-8 Effect of Thermal Acceleration on the Degradation of Gallium doped Zinc Oxide Thin Film
J. Kang, M. Lee, H. Choi, W. Seo (Korea Institute of Ceramic Engineering and Technology, Korea); D.Y. Lee (Daelim College of Technology, Korea)
Transparent conducting Oxides (TCO) thin films such as indium tin oxide (ITO) and zinc oxide (ZnO) have been widely studied for their practical applications as transparent electrodes, solar cell and various opto-electronics. However, because of the high cost and scarcity of indium, transparent conducting ZnO has recently attracted much attention as a promising alternative material. Undoped ZnO thin films are not stable especially at high temperature, doping the zinc oxide can reduce this disadvantage. ZnO doping is achieved by replacing Zn2+ atoms with atoms of element of high valence such as aluminum, gallium. But, Gallium element has more advantages than Al element because the size of Ga ion as impurities is similar to size of zinc ion, minimizing lattice defect. Through several researches, electrical properties of doped ZnO thin film has secure closely ITO. However, TCO Thin films go through various thermal processes and environmental condition where these could be a ffected by heat. In this research, the effect of thermal degradation on Ga doped zinc oxide (GZO) thin film was studied in higher accelerated conditions of temperature. GZO thin film was prepared by R.F sputtering using ZnO target doped with 5wt% of Gallium. The prepared GZO films were exhibited thickness of 150nm, resistance of 30~40Ω/sq and transmittance of 90%. The percentile increment of resistance by thermal acceleration exceeded 15% after 26.9hr, 2.8hr, 0.1hr at 200C, 250C, 300C, respectively. Surface roughness (Ra) of GZO film increased to 10times by thermal condition. The acceleration factor and the activation energy of degradation were calculated.
CP-9 Linear and Nonlinear Optical Properties of CdSe/PMMA Nanocomposite Filters with Mechanical Property Improvement
G. Chen (University of Arkansas); Y.A. Wang (Ocean NanoTech, LLC.); M. Xiao, M. Zou (University of Arkansas)
Hybrid composites of CdSe nanocrystals embedded in poly(methyl methacrylate) (PMMA) matrices were prepared by casting methods which disperse the quantum dot powder and PMMA in chloroform solution. X-ray diffraction (XRD) measurements of the CdSe/PMMA nanocomposites show broad pattern for cubic CdSe. The particle size of CdSe estimated from XRD measurements is 8.5 nm. UV-vis absorption spectra and refractive index measurements of the nanocomposites show that the linear optical properties of the nanocomposite films are strongly dependent on the CdSe nanocrystal concentration in the PMMA polymer. The room temperature nonlinear optical properties of the nanocomposites were investigated using a single-beam Z-scan technique with femtosecond laser pulses at the wavelengths of 794 nm. The experimental data reveals that the optical nonlinearity varies with the input laser energy as well as the concentration of the CdSe nanocrystal in the polymer. In addition, mechanical property characterization results show that both the Young’s modulus and the hardness of the nanocomposite film increase as the concentration of CdSe nanocrystal in the PMMA polymer increases. The results of this study indicate that CdSe/PMMA nanocomposite films, having favorable nonlinear optical properties while in the mean time possessing improved mechanical properties than pure PMMA, are promising material for optical filter applications.
CP-10 Influence of Sputtering Gas on the Properties of Reactively Sputtered Tungsten Oxide Films
A.K. Chawla, S. Singhal, R. Chandra, H.O. Gupta (Indian Institute of Technology Roorkee, India)
Due to high refractive index and chemical stability characteristics, tungsten oxide (WO3) thin films were used in a wide range of optical, electrical and chemical applications such as electrochromic devices, solar cells, photo catalysts, antireflective coating and chemical sensors. Considering the field of optical applications, the basic requirements of fabricated thin films are homogeneous, non-porous, high packing density and low optical loss. Depending on the deposition conditions and synthesis techniques films may present considerably different structural, optical and electrical behavior, and consequently different electro chromic behavior. With DC magnetron sputtering thin film properties can be improved by controlling the reactive gas atmosphere. Bandgap values from 2.6 to 3.4 eV, reported for polycrystalline and amorphous WO3 thin films, only allow for absorption in the near ultraviolet and blue region of the solar spectrum. Bandgap modifications woul d be necessary to extend the light harvesting capability to a wider portion of the solar spectrum. Bandgap modification of WO3 films through doping techniques is proposed. In this work, nitrogen doping was used to modify structural and, optical, properties of the material in the presence of two inert gases (Argon and Helium). Tungsten oxide films were produced using reactive dc magnetron sputtering. Substituting Helium gas in place of argon results in a decrease in the particle sizes and thus affects the band gap values. Crystal structure and surface morphology were studied by X-ray diffraction (XRD) and atomic force microscope (AFM), respectively. We find that the atomic mass of the sputtering gas significantly affects the primary crystallite size as well as the surface morphology and texture. Optical properties were studied using UV-Vis-NIR spectrophotometer in the visible spectrum.
CP-11 Modulation of Luminescence Emission Spectra of N-Doped Ga2O3 Nanowires by Thermal Evaporation
L.-W. Chang (National Tsing Hua University, Taiwan); M.W. Huang, C.-F. Li (National Chung Hsing University, Taiwan); J.-W. Yeh (National Tsing Hua University, Taiwan)

In this study, we have synthesized N-doped Ga2O3 nanowires on a p-type Si (100) substrate with N2 (50 sccm) and O2 (1 sccm) at 800°C through a two-step evaporation to modulate the spectra of the luminescence emission. Both TEM and XRD analyses confirmed that N-doped Ga2O3 is monoclinic with a uniform mean diameter of 40 nm and a length up to several tens of micrometers. As determined by selected area diffraction (SAD), the growth direction of N-doped Ga2O3 nanowires is [002]. The optical properties of the N-doped Ga2O3 nanowires were studied by photoluminescence (PL) at the room temperature, exhibiting a red-light (738nm) and near infrared-light (805nm) emissions as a function of the nitrogen dopant in response to Ar-Kr laser excitation at 532nm. The results serve to reinforce the potential of N-doped Ga2O3 nanowires for optoelectronic device applications.

1 Laurent Binet and Didier Gourier, J. Phys. Chem. Solids. 59 (1998) 1241

2 Y. P. Song, H. Z. Zhang, C. Lin, Y. W. Zhu, G. H. Li, F. H. Yang, and D. P. Yu, Phys. Rev. B 69 (2004) 075304

3 Pai-Chun Chang, Zhiyong Fan, Wei-Yu Tseng, A. Rajagopal, and Jia G. Lu, Appl. Phys. Lett. 87 (2005) 222102

*The research is supported by the Republic of China National Council Grant No. NSC 96-2221-E-034-006-MY2 and No. NSC 95-2221-E-034-020-MY2.
CP-13 Characterization of Anomalous Luminescence Properties from Self-Ordered Porous Anodic Alumina with Oxalic Acid Electrolytes
Y.-R. Chen, C.-H. Fang (National United University, Taiwan); J.-C. Wang, T.-E. Nee (Chang Gung University, Taiwan)
In recent years, self-ordered porous anodic alumina (PAA) film have been extensively used as templates, mask, or host materials to synthesize various nanostructures, and building blocks for developing nanoscale devices. PAA film produced by the anodization technique has a nanoscale porous structure in mass production and the pore height and diameter are controllable and was applied in the fabrication of visible spectral range optical devices. In order to characterize the luminescence properties, we have formed the self-ordered PAA films which evaporated onto silicon substrates. In this work, the anomalous luminescence properties of carrier confinement in PAA films have been investigated by introducing oxalic acid electrolyte into the anodization technique. The temperature-dependent photoluminescence (PL) spectra were measured to characterize the recombination mechanisms. From the PL spectra of PAA films, it has found the asymmetrical luminescence profile in the blue emi ssion region. It was used the Gaussian function to divided into two subbands which originate in two kinds of different oxygen-deficient defect centers, i.e., F+ (oxygen vacancy with only one electron) and F (oxygen vacancy with two electrons) centers, respectively. The density of the F centers is the largest on the surface, followed by a gradual decrease with an increase in the pore wall depth and electrolyte concentration. However, it was observed the reverse trend of the F+ centers. In strong contrast to a commonly expected trend of uniformly reduced non-radiative recombination with decreasing the lattice temperature, anomalous low-temperature PL growing and declining is observed between the F and F+ centers. The rate equation models are invoked to corroborate the anomalous temperature behaviors. All the calculations are agreement with the experimental observations. The temperature-dependent lifetimes for the PAA films will be discussed in detail as well.
CP-14 Enhancement of Light Reflectance and Thermal Stability in Ag-Mg Alloy Contacts on p-Type GaN
Y.H. Song, G.H. JUNG, J.H. Son, J.-L. Lee (Pohang University of Science and Technology (POSTECH), Korea)
Recently, flip-chip and vertical-structure designs were exploited in GaN-based LEDs to improve the light extraction efficiency. In these configurations, highly reflective p-Ohmic contacts must be essential for increasing light extraction efficiency. Silver (Ag) has been widely used for a reflective ohmic contact due to its high reflectance (>95%) for visible light and low electrical resistivity. However, agglomeration has been observed at high temperature and considered as a weak point of Ag contact. The agglomeration of Ag film affects the electrical resistivity and optical properties of device operation. Therefore, preventing Ag from oxidation and/or agglomeration is a key aspect in obtaining high quality Ag-based ohmic contacts. Until now, several efforts to improve the thermal stability of Ag-based ohmic contacts have been demonstrated such as Ag-Al alloy and Ag-Cu alloy contact. However, degradation of electrical and optical properties was still found in these allo y-based ohmic contacts. In this presentation, we investigated Ag-Mg alloy contact as a method to prevent agglomeration of Ag contact on GaN at elevated temperatures. Changes in surface morphology and micro-structure in both Ag and Ag-Mg alloy contacts (0.1 wt.% Mg) were investigated using AFM, SEM, and XRD. Interfacial reactions between contact metals and GaNwere analyzed using depth profiles of secondary ion mass spectroscopy and synchrotron radiation photoemission spectroscopy. Based on these experimental results, the effects of Mg addition to Ag on the electrical and optical properties of the contact are proposed. Ag-Mg alloy contact was developed for obtaining low contact resistivity and high reflectance ohmic contacts on p-type GaN. Specific contact resistivity of 2.0 х 10-5cm2 and light reflectance of 82% on sapphire were achieved from Ag-0.1 wt.% Mg alloy contact after annealing at 400oC in air. Because Mg atoms in Ag matrix have high diffusivity and low oxidation Gib bs formation energy, Mg atoms in Ag matrix move to surface of Ag-Mg alloy contact. This suggests that oxidized-Mg overlayer can be formed on the surface during the thermal annealing process in an air ambient. These oxidized-Mg overlayer could act as a diffusion barrier for excessive incorporation of oxygen into the Ag layers with the transformation into MgO. As a result, oxidized Mg atoms on Ag-Mg alloy contact induced the good thermal stability in Ag-Mg alloy contact, preventing Ag agglomeration.
CP-15 Electrochromic Tungsten-Titanium Oxide Films Deposited by Co-Sputtering using a Pulsed Sputtering Deposition System
K.-W. Weng (Mingdao University, Taiwan); S. Han (National Taichung Institute of Technology, Taiwan); Y.-C. Chen (National Chung Hsing University, Taiwan)
Titanium doped tungsten oxide films deposited by co-sputtering metallic titanium and tungsten using a pulsed sputtering deposition system. The pulse power was varied in the range 100 to 500 W keeping the gas flow rate and pulsed frequency. The films are amphorous or microcrystalline depending on the pulse power. The XRD results show that for low pulse power the films present an amphorous tungsten trioxide, while for high pulse power (about 400 W) they present a mixture of a more crystalline. The XPS examination showed the existence of +6 valence tungsten ions and +4 valence titanium ions. The as deposited films with 400 W are transparent with transmittance exceeding 70% in the near-IR region. An in situ three electrode cell with a 0.1 M lithium perchlorate/propylene carbonate electrolyte was used. It is a good electrochromic behavior at an optimal pulse power 400W.
CP-16 Deposition and Post-Deposition Treatment for Obtaining Sco on Si and Quartz Substrate
J.L. Deschanvres, A. Khan, H. Roussel, C. Jimenez (INP Grenoble-Minatec, France); B. Servet (Thales Research & Technology, France); M. Modreanu (Tyndall National Institute, Ireland)
Divalent ions in a copper oxide matrix M+2Cu2O2 have been intensively studied for the application field of p-type Transparent Conductive Oxide (TCO) in order to design transparent electronic devices. To achieve this goal, we are working on the deposition of SrCu2O2 (SCO) on Si and quartz substrates by Metal-Organic Chemical Vapor Deposition (MOCVD) techniques. Among the p-type TCOs, SCO is one of the most promising candidates for the use in optoelectronic devices. The MOCVD technique was selected because of its high deposition rate, large area deposition, low price and high facility of precursors preparation in different ratios. The precursors selected for this purpose were Strontium and Copper tetramethylheptadionate (TMHD)2 and the solvent used was meta-xylene. For all the depositions in the temperature range (480°C-570°C), the FTIR and XRD analysis show that the as-deposited films do not contain SCO phase, rather it is composed of a mixture of Copper oxide (CuO) and Strontium carbonates (SrCO3). The formation of CuO and SrCO3 is due to low deposition temperature and can be eliminated at higher deposition temperature, but the deposition temperature higher than 570°C affects the visual aspect of the film and the film become more and more diffusive at higher and higher deposition temperatures. Therefore, some post-deposition treatments were performed in order to burn the carbonates and achieve the SCO phase. The post-deposition treatment was also necessary to crystallize the film because the as-deposited film was almost amorphous. As a first step the film was annealed under O2 atmosphere at 600°C and a new phase SrCu2O3 was obtained . The analysis by XRD and FTIR revealed the SrCO3 was completely eliminated. In the second step, the film was annealed under the same condition in Ar atmosphere and it was found that SrCO3 is completely converted into pure SCO thin film. The annealing was performed in two different ways; the Rapid Thermal Annealing (RTA) and Conventional Annealing. The RTA was performed for 30 seconds at 600°C for each O2 and Ar step for samples deposited on Si substrates. For conventional annealing the duration of annealing was 1 hour and 30 minutes for each sample deposited on Si and quartz substrate.
Time Period ThP Sessions | Topic C Sessions | Time Periods | Topics | ICMCTF2009 Schedule