Highly c-axis oriented Na0.5K0.5NbO3 (NKN) films have been prepared on thermally grown thin SiO2 template layer onto Si(001) wafer by pulsed laser deposition technique. X-ray diffraction ø-2ø-scan data show multiple-cell structuring along the polar axis in NKN films grown onto SiO2 with thickness up to 45 nm. On the other hand, the film deposited onto amorphous ceramic (Coming) glass is a mixture of slightly c-axis oriented NKN and pyrochlore phases, while the film onto Pt(lll)/Ti/SiO2/Si(001) shows perfect [111] orientation. This implies small amount of SiO2 crystallites distributed in amorphous silica matrix inherits Si(001) orientation and serves as a key factor in highly oriented growth of NKN films. Au upper electrodes have been defined on the top of NKN(270nm)/SiO2/Si structures to investigate Metal-Ferroelectric-Insulator-Silicon (MFIS) diode characteristics for Field Effect Transistor (MFIS-FET) nonvolatile memory applications. C-V measurements yield memory window of 4.14 V at 10 V of gate voltage.

We grew BaxSr1−xTiO3 (BST) films on MgO single crystal substrates by pulsed laser deposition (PLD). We report the in-plane (a) and out-of-plane (c) lattice parameters of BST films deposited in a range of O2 deposition pressures [P(02)], as measured by asymmetric rocking curve diffraction. As P(O2) increases, the films' biaxial strain changes from compression (a < c), to cubic (a = c), and then to tension (a > c). Furthermore, both a and c are larger than the lattice constant for bulk BST of the same composition. This indicates the presence of a hydrostatic strain component in addition to the biaxial component. From the measured lattice parameters, we calculate the total residual strain in terms of biaxial and hydrostatic components. We also examine the effects of a post-deposition anneal. Characterizing residual strain and understanding its origin(s) are important since strain affects the dielectric properties of BST films and thereby the properties of devices which incorporate them.

Light scattering investigations are carried out on BaBi4Ti4O15 (BBiT) which is a member of the Bi-layer structure ferroelectric oxide with n = 4. The BBiT thin films, thickness ∼ 300 nm, were grown on epitaxial conducting LaNiO3 electrodes on epitaxial buffer layers on (100) silicon by pulsed laser deposition. Micro-Raman measurements performed on these films reveal a sharp low-frequency mode at 51 cm−1 along with broad highfrequeficy modes corresponding to other lattice vibrations including TiO6 octahedra. No temperature dependence of the low frequency mode is seen while a weak dependence of the broad high frequency vibrations are observed in the mixed oriented regions. Raman polarization carried out at room temperature indicates that the prominent modes have Alg and Eg symmetries in the BaBi4Ti4O15 thin films.

Epitaxial, ferroelectric Ba2Bi4Ti5O18 films grown on LaNiO3/CeO2/ZrO2:Y2O3 epitaxial layers on Si(100) are investigated by cross-section high-resolution transmission electron microscopy (HRTEM). The films are perfectly oriented and consist of well-developed grains of rectangular shape. The grain boundaries are strained and contain many defects, especially a new type of defect, which can be described as a staircase formed by repeated lattice shifts of Δ ∼ c/12 ∼ 4.2 Å in the [001] direction. This repeated shift results in seemingly bent ribbons of stacked Bi2O2 planes, involving, however, individual Bi2O2 planes which remain strongly parallel to the (001) plane. These defects contain an excess of bismuth. Other defects found in the grain interior include mistakes in the stacking sequence originating from the presence of single, well-oriented, non-stoichionietric layers intergrown with the stoichiometric Ba2Bi4Ti5O18 film matrix.

Ba(Ti,Zr)O3 thin films were grown hydrothermally on silicon substrates coated with sputtered a Ti-34 at.%Zr metallic alloy thin film. To ensure the formation of Ba(Ti,Zr)O3 under the hydrothermal conditions at 150°C, the concentration of the Ba(OH)2 had to be greater than 0.25 M. Preliminary capacitance measurement revealed a dielectric constant of 200 in Ba(Ti,Zr)O3 films of approximately 320 nm. The formation mechanism is discussed.

Thin films of PZT were deposited onto platinized and bare single crystal NaCl using spin coating and sol-gel precursors. These films were then analyzed using in situ heating in a transmission electron microscope. The results of in situ heating are compared with those of an ex situ heat treatment in a standard furnace, mimicking the heat treatment given to entire wafers of these materials for use in MEMS and ferroelectric applications. Films are shown to transform from amorphous to nanocrystalline over the course of days when held at room temperature. While chemical variations are found between films crystallized in ambient conditions and films crystallized in the vacuum conditions of the microscope, the resulting crystal structures appear to be insensitive to these differences. Significant changes in crystal structure are found at 500°C, primarily the change from largely amorphous to the beginnings of clearly crystalline films. Crystallization does occur over the course of weeks at room temperature in these films. Structural changes are more modest in these films when heated in the TEM then those observed on actual wafers. The presence of Pt significantly influences both the resulting structure and morphology in both in situ and ex situ heated films. Without Pt present, the films appear to form small, 10 nm grains consisting of both cubic and tetragonal phases, whereas in the case of the Pt larger, 100 nm grains of a tetragonal phase are formed.

Solid solution films of the σ-Fe2O3-FeTiO3 series are one of the candidates for noble half-metallic oxides. They were epitaxially formed on σ-Al2O3(001) single crystalline substrates by O2 -reactive evaporation method. The Fe2−x TixO3+σ films prepared at higher Ts=973 K and with larger Ti content x≤0.4 had the ilmenite structure with R3 symmetry. Other films at lower Ts or with smaller x possessed the corundum structure with R3c. Only the films with R3 symmetry had large ferrimagnetic moments, though the observed spontaneous magnetization was less than half of the ideal value expected from the fully ordered structure. Room temperature resistivity of intermediate composites dropped to 10−lΔcm due to the formation of the mixed valence states between Fe2+ and Fe3+. However the Fe2+ content of the films was rather small as compared with stoichiometric Fe2−xTixO3. The Ti-rich films had large oxygen nonstoichio netry of about σ=0.3.

Increasingly large-volume markets for large-area, flat-panel displays and photovoltaic panels are likely to be established in the early years of the next century and transparent conducting oxides (TCOs) of improved opto-electronic properties will be required to enable some of these applications to be realized. Our work is focusing on improving both the fabrication-limited properties of the materials (extrinsic), and materials-limited properties (intrinsic). The emphasis on achieving improved electrical and optical properties hinges on achieving higher electron mobility via intrinsic and/or extrinsic properties. To this end, we have investigated the properties of several TCOs including cadmium oxide, tin oxide, zinc oxide, cadmium stannate and zinc stannate. These may be deposited by chemical vapor deposition (CVD) or sputtering and we hope to establish the capability to fabricate compounds and alloys in the cadmium oxide, tin oxide, zinc oxide ternary phase diagram.

The properties of the materials have been investigated using a wide variety of techniques including high-resolution electron microscopy, atomic force microscopy and X-ray diffraction, as well as Mössbauer, Raman and UV/visible/NIR spectroscopies. We have measured the transport properties (conductivity, Hall, Seebeck and Nernst coefficients) and have obtained the effective mZLss, relaxation time, Fermi energy, and scattering parameter. This information has been obtained as a function of carrier concentration, which depends on the deposition and annealing procedures. We have found that the mobilities of free-electrons in the cadmiumbearing compounds are greatly superior to those in the other materials, because they have much longer electron relaxation times. In the case of cadmium oxide, there is also great benefit from a much lower effective mass. We are gaining a clearer understanding of the fundamental microscopic attributes needed for TCOs, which will be required in more-demanding, and rapidly emerging, applications.

Transparent and conductive thin films using new multicomponent oxides consisting of a combination of different In2O3 based ternary compounds have been prepared on room temperature substrates by r.f. magnetron sputtering. Transparent and conductive (Ga,In)2O3-MgIn2O4, (Ga,In)2O3-Zn2In2O2, (Ga,In)2O3-In4Sn3O12, Zn2In2O5,-In4Sn3O12 and Zn21n2O5-MgIn2O4 films were prepared over the whole range of compositions in these multicomponent oxides. The electrical and chemical properties of the resulting films could be controlled by varying the composition in the target. The resistivity, band-gap energy, work function and etching rate of the resulting multicomponent oxide films ranged between the properties of the two ternary compound films. This paper also presents a discussion of a significant spatial distribution of resistivity found on the substrate of the multicomponent oxide films as a function of composition. The resistivity distribution is attributable to the oxygen concentration on the substrate surface rather than the bombardment effect of high energy particles.

We have investigated the electronic structures of p- or n-type doped ZnO based on ab initio electronic band structure calculations in order to control valence states in ZnO for the fabrication of low-resistivity p-type ZnO. We find unipolarity in ZnO; p-type doping using Li or N increases the Madelung energy while n-type doping using Al, Ga, In or F species decreases the Madelung energy. We have proposed materials design: codoping using N acceptors and reactive codopants, Al or Ga, enhances electric properties in p-type codoped ZnO. It has been already verified by experiments using the N acceptors and Ga reactive donor codopants. We find a very weak repulsive interaction between Li acceptors and the delocalization of the Li-impurity states for Lidoped ZnO, in contrast with the case of N-doped ZnO. On the other hand, we find the compensation mechanism by the formation of 0 vacancy in the vicinity of the Li-acceptor sites. We propose a group VII element, F species, as a promising candidate for use of the reactive codopant as for Li-doped ZnO in order to realize low-resistivity p-type ZnO.

Thin films of CuAlO2, CuGaO2 and AglnO2 with delafossite structure were prepared on sapphire substrates by pulsed laser deposition method. The resulting CuA102 thin films exhibited p-type conduction and the electrical conductivity at room temperature was 0.3 Scm−1. CuGaO2 thin films were grown epitaxially on μ-Al2O3 (001) surface and showed p-type conduction (conductivity at room temperature = 0.06 S cm−1). The optical band gap was estimated to be ∼3.5 eV for CuAlO2 or ∼3.6 eV for CuGaO2. On the other hand, the thin film of Sn doped AglnO2 exhibited n-type conduction. The optical band gap and electrical conductivity at room temperature were ∼4.1 eV and 70 S cm−1, respectively. The recent work demonstrates the validity of our chemical design concept for p- and n-type transparent conducting oxides, providing an opportunity for realization of transparent p-n junction using delafossite-type oxides.

The crystallization of amorphous indium oxide thin films with zero to 9.8 wt% SnO2, was studied using a combination of in situ MOSS (multibeam optical stress senor) and in situ resistivity measurements. We report that amorphous indium oxide deposited using electron beam evaporation undergoes crystallization in a two part process of amorphous structure relaxation followed by crystallization. MOSS measurements show that the relaxation process corresponds to a densification of the amorphous structure while crystallization results in a molar volume increase.

High quality ITO thin films were grown hetero-epitaxially on extremely flat substrate of (001) YSZ by a pulsed laser deposition technique at a substrate temperature of 600°C. The crystal orientation relationship between the film and YSZ were confirmed as ITO (001) // YSZ (001) and ITO (010) // YSZ (010), respectively, by HR-XRD and HR-TEM. The carrier densities of the films were almost equal to Sn02 concentration in the films. That is, almost all the doped Sn4+ ions were activated to release electrons to the conduction band. The carrier densities of the films were enhanced up to 1.9×1021cm−3, while the Hall mobility showed a slight, almost linear, decrease from 55 to 40cm2V−1s−1 with increasing SnO2 concentration. The low resistivity is due to larger electron mobility, which most likely resulted from good crystal quality of the films. The optical transmissivity of the film exceeded 85% at wavelengths from 340 to 780nm.

Transparent conducting oxides (TCO) have relatively low mobilities, which limit their performance optically and electrically, and which limit the techniques that may be used to explore their band structure via the effective mass. We have used transport theory to directly measure the density-of-states effective mass and other fundamental electronic properties of TCO films. The Boltzmann transport equation may be solved to give analytic solutions to the resistivity, Hall, Seebeck, and Nernst coefficients. In turn, these may be solved simultaneously to give the density-of-states effective mass, the Fermi energy relative to either the conduction or valence band, and a scattering parameter, s, which characterizes the relaxation time dependence on the carrier energy and can serve as a signature of the dominate scattering mechanism. The little-known Nernst effect is essential for determining the scattering parameter and, thereby, the effective scattering mechanism(s). We constructed equipment to measure these four transport coefficients on the same sample over a temperature range of 30 – 350 K for thin films deposited on insulating substrates. We measured the resistivity, Hall, Seebeck, and Nernst coefficients for rf magnetron-sputtered aluminum-doped zinc oxide. We found that the effective mass for zinc oxide increases from a minimum value of 0.24me, up to a value of 0.47me, at a carrier density of 4.5 × 1020 cm−3, indicating a nonparabolic conduction energy band. In addition, our measured density-of-states effective values are nearly equal to conductivity effective mass values estimated from the plasma frequency, denoting a single energy minimum with a nearly spherical, constant-energy surface. The measured scattering parameter, mobility vs. temperature, along with Seebeck coefficient values, characterize ionized impurity scattering in the ZnO:AI and neutral impurity scattering in the undoped material.

CuAlO2 is one of several materials currently being investigated for application as a p-type transparent conducting oxide. In this paper we report a method of making c-axis oriented CuAlO2 thin films which eliminates previously reported phase-purity and surface morphology problems. Thin film precursors of CuA1O2 were deposited on YSZ (100) substrates by roomtemperature radio frequency sputtering. Subsequent annealing in 10mT of oxygen at temperatures as low as 800°C resulted in phase-pure, textured CuAlO2. The films were p-type and transparent with a gap of 3.5eV, but typical carrier concentrations were low (on the order of 1016 cm−3). Oxygen anneals at 700°C in 1 atm of O2 raised this to 1018 cm−3 in some samples. In order to increase the carrier concentration further, we are testing chemical substitution on the metal sublattice. Initial experiments were done with Mg as a dopant, either by direct solid-state synthesis for bulk materials or by alternating deposition of MgO and CuAlO2 during the pulsed laser deposition of thin films. At Mg molar concentrations of 1% or less, the bulk material was phase-pure CuAlO2 by x-ray diffraction, but was mixed-phase CuAl2O4 and CuO when the Mg concentration was increased to 2%. Thin films sputtered from the 1% Mg substituted target crystallized to CuA102 after a 940°C anneal at 10T 02, but were more than 30 times more resistive than the undoped films.

This paper reports on progress in the fabrication of IR-transparent electrically conductive copper aluminum oxide (CuAlxOy) by reactive magnetron co-sputtering from high-purity-Cu and -Al targets in an argon-oxygen-gas mixture. Recent equipment modifications have resulted in much better control of deposition parameters like forward and reflected power and, consequently, much better control of film composition. Applying the correct amount of power to each target and adjusting the oxygen-partial pressure have significantly reduced the growth of surface-oxide layers on the metal targets. Equipment and process improvements have eliminated the sputterrate inconsistencies and arcing that led to lack of composition control in our earliest films. We now have much better control of film composition and are beginning to understand the relationship between the electro-optical properties and the molecular structure of the films using Fourier transform infrared (FTIR) spectroscopy, electron spectroscopy for chemical analysis (ESCA), inductively coupled plasma (ICP) emission spectroscopy, high resolution electron microscopy (HREM) and electron energy loss spectroscopy (EELS). A pair of weakly intense FTIR absorption bands at 1470 and 1395cm−1 is present in films that have enhanced electrical conductivity and IR transparency. Understanding the origin of these bands could speed development of CuAlO2 as a wide-bandgap-conductive oxide since these bands are clearly associated with enhanced conductivity and carrier mobility. The best film to date transmits about 80% in the mid-wave IR and has a sheet resistance of 160Δ;/sq.

The characteristics of indium tin oxide (ITO) films grown at room temperature on (100) Si and Corning glass substrates by an in situ ultraviolet-assisted pulsed laser deposition (UVPLD) technique have been investigated. The most important parameter, which influenced the optical and electrical properties of the grown films, was the oxygen pressure. For oxygen pressure below 1 mtorr, films were metallic, with very low optical transmittance and rather high resistivity values. The resistivity value decreased when using higher oxygen pressures while the optical transmittance increased. The optimum oxygen pressure was found to be around 10 mtorr. For higher oxygen pressures, the optical transmittance was better but a rapid degradation of the electrical conductivity was noticed. X-ray photoelectron spectroscopy investigations showed that ITO films grown at 10 mtorr oxygen are fully oxidized. All of the grown films were amorphous regardless of the oxygen pressure used.

Room temperature operation of UV LED is realized for the first time using a hetero p-n junction composed of transparent conductive oxides, p-SrCu2O2 and n-ZnO. Ni/SrCu2O2/ZnO/ITO multi-layered film was epitaxially grown on an extremely flat YSZ (111) surface by a PLD. The grown films were processed by a conventional photolithography, followed by reactive ion etching to fabricate p-n junction diode. The resultant device exhibited rectifying I-V characteristics inherent to p-n junction whose turn-on voltage was about 1.5V. A relatively sharp electro-luminescence band centered at 382nm was generated when applying the forward bias voltage larger than the turn-on voltage of 3V. The red shift in the EL peak was noticed from that of photo-luminescence (377nm), which was most likely due to the difference in the excited state density between the emission processes. The EL band is attributed to transition in ZnO, probably to that associated with electron-hole plasma. The photo-voltage was also generated when the p-n junction was irradiated with UV light of which energy coincided with both exciton and band-to-band transitions in ZnO.

Oxygene ions diffusitives in tin dioxide based thin films were measured with electrochemical method. The Pd content 0-3% at. thin films were investigated. The dependencies of the diffusitives vs. content of the layer were obtained.

Novel amorphous transparent conductive oxides, InGaO3(ZnO)m, where m is an integer less than four, was developed. Optical transmittance in the visible region exceeded over 80 % and the electric conductivity at 300 K was as large as 400 S/cm. Both Seebeck and Hall coefficients exhibited negative values, indicating the conduction was n-type. It was suggested that 4s orbital of Zn2+ played a significant role for the formation of the extended state responsible for the conduction, while In3+ acted as a modifier for the stabilization of amorphous state.