Activation energy of water vapor and oxygen transmission through TiNxOy/PET gas barrier films

Titanium oxynitride (TiN_xO_y) films were deposited on polyethylene terephthalate (PET) substrates by means of a reactive radio frequency (RF) magnetron sputtering system in which the power density was the varied parameter. Experimental results show that the deposited TiN_xO_y films with a thickness of about 55 nm have similar contents of TiN, TiN_xO_y and TiO₂ bonds, although they are deposited at different power densities. The TiN_xO_y films deposited at a lower power density have fewer internal defects and grain boundaries and possess higher activation energy and a lower rate of water vapor and oxygen transmission through TiN_xO_y/PET films.     

Field electron emission from HfNxOy thin films deposited by direct current sputtering

HfN_xO_y thin films were deposited on Si substrates by direct current sputtering at room temperature. The samples were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray diffraction (XRD). SEM indicates that the film is composed of nanoparticles. AFM indicates that there are no sharp protrusions on the surface of the film. XRD pattern shows that the films are amorphous. The field electron emission properties of the film were also characterized. The turn-on electric field is about 14 V/μm at the current density of 10 μA/cm², and at the electric field of 24 V/μm, the current density is up to 1 mA/cm². The field electron emission mechanism of the HfN_xO_y thin film is also discussed.     

Electrical behaviour of SiOxNy thin films and correlation with structural defects

Silicon oxynitride thin films were deposited by reactive r.f. sputtering from a silicon target. Different Ar:O₂:N₂ gas atmospheres were used at fixed power density (3.18 W cm⁻²) and pressure (0.4 Pa) to obtain various film composition. Pt-SiO_xN_y-Pt sandwich type structure was realised for electrical property investigations. The C-V measurements showed the absence of a Schottky barrier and thus confirmed that Pt electrode provides an ohmic contact. The evolution of the current density showed a decrease of the film conductivity when the oxygen concentration in the films increases. The various layer composition leads to two different conduction mechanisms which were identified as space charge limited current (SCLC) and Poole-Frenkel effect. Finally, the structural defects of the films were studied by EPR analysis and the spin densities were correlated to both the composition and the electrical behaviour of the films.     

Laser synthesis of semiconductor nanostructures with narrow band gap

Semiconductor nanostructures with narrow band gap were synthesized by means of laser chemical vapor deposition (LCVD) of elements from iron carbonyl vapors [Fe(CO)₅] under the action of Ar⁺ laser radiation (λ_L = 488 nm) on the Si substrate surface. The temperature dependence of the specific conductivity of these nanostructures in the form of thin films demonstrated typical semiconductor tendency and gave the possibility to calculate the band gap for intrinsic conductivity (E_g) and the band gap assigned for impurities (E_i), which were depended upon film thickness and applied electrical field. Analysis of deposited films with scanning electron microscopy (SEM) and atomic force microscopy (AFM) demonstrated their cluster structure with average size not more than 100 nm. Semiconductor properties of deposited nanostructures were stipulated with iron oxides in different oxidized phases according to X-ray photoelectron spectroscopy (XPS) analysis.These deposited nanostructures were irradiated with Q-switched YAG laser (λ_L = 1064 nm) at power density about 6 × 10⁷ W/cm². This irradiation resulted in the crystallization process of deposited films on the Si substrate surface. The crystallization process resulted in the synthesis of iron carbide-silicide (FeSi_2−xC_x) layer with semiconductor properties too. The width of the band gap E_g of the synthesized layer of iron carbide-silicide was less than for deposited films based on iron oxides Fe₂O_3−x (0 ≤ x ≤ 1).     

Electrical and optical properties of ZnO films prepared by sputtering of ZnO targets containing AlN

ZnO films prepared from the ZnO target containing 2% AlN are transparent irrespective of radio frequency (RF) power. The obtained ZnO films have the carrier density of 3.8 × 10²⁰ cm⁻³ or less and the low mobility of 5.3-7.8 cm²/(V s). In the case of 5% AlN target, ZnO films prepared at 40, 60 and 80 W are transparent, whereas ZnO films prepared at 100 and 120 W are colored. As RF power increases from 40 to 120 W, the carrier density increases straightforwardly up to 5.5 × 10²⁰ cm⁻³ at 100 W and is oppositely reduced to 3.2 × 10²⁰ cm⁻³ at 120 W. In the case of 10% AlN target, ZnO films prepared at 60 W or more are colored, and have the carrier density of 4 × 10²⁰ cm⁻³ or less. The N-concentration in these colored films is estimated to be 1% or less. The Al-concentration in the ZnO films prepared from the 5 and 10% AlN targets is higher than 2%. The carrier density of the ZnO films containing Al and N atoms is nearly equal to that of ZnO films doped with Al atoms alone. There is no evidence in supporting the enhancement of the carrier density via the formation of N-Al_xZn_4−x clusters (4 ≥ x ≥ 2).     

Nd-laser irradiations effects and AFM-investigations on structural and surface features of optimally lutetium thorium-co-doped-2212-BSCCO

Lutetium-thorium optimally co-doped sample with general formula Bi_2−x−yLu_xTh_ySr₂Ca₁Cu₂O₈ where x = y = 0.15 mol was selected to be the target for three different doses of Nd-laser beam irradiations the 1st 15 W/cm² for 60 min, 2nd 30 W/cm² for 120 min and 3rd 45 W/cm² for 240 min, respectively. Nd-Laser irradiations doses were monitoring as function of micro-structure, superconducting and structural features of Lu-Th-optimally co-doped 2212-BSCCO. AFM and SE-microscopy were applied to investigate changes occurred in the surface's layers after each Nd-laser irradiation dose. Both of bulk superconductivity and surface resistivity were measured to establish the promotion occurred on the superconducting features due to Nd-laser irradiation doses.     

Effects of substrate bias and nitrogen flow ratio on the surface morphology and binding state of reactively sputtered ZrNx films before and after annealing

ZrN_x films were sputtered in an Ar + N₂ atmosphere, with different substrate biases (0 to −200 V) at various nitrogen flow ratios (%N₂ = 0.5-24%). The surface morphology, resistivity, crystllinity, and bonding configuration of ZrN_x films, before and after vacuum annealing, were investigated. As compared with ZrN_x films grown without substrate bias, before and after annealing, the resistivity of 1% and 2% N₂ films decreases with increasing substrate biases. Simultaneously, if the applied bias is too high, the crystallinity of ZrN_x film will decrease. The surfaces of 1% and 2% N₂ flow films deposited without bias have small nodules, whereas the surface morphology of films deposited at −100 V of substrate bias exhibits large nodules and rugged surface. Once a −200 V of substrate bias is applied to the substrate, the surface morphology of ZrN_x films, grown at 1% and 2% nitrogen flow ratios, is smooth. Furthermore, there are two deconvoluted peaks in XPS spectra (i.e., Zr-O and Zr-N) of ZrN_x films deposited at −200 V of substrate bias before and after annealing. On the other hand, the surface morphology changes dramatically from rugged surfaces for film deposited at lower nitrogen flow ratio (%N₂ < 1%) to smoother and denser surfaces for film grown at higher nitrogen flow ratio (%N₂ ≥ 1%). The Zr-N bonding in 2% N₂ films still exist after annealing at 700 °C, while the Zr-N bonding in 0.5% and 16% N₂ flow film vanish at the same temperature. The connection between the resistivity, crystallinity, surface morphology, and bonding configuration of ZrN_x films and how they are influenced by the substrate bias and nitrogen flow ratio are discussed in this paper.     

X-ray multiple diffraction in the characterization of TiNO and TiO2 thin films grown on Si(0 0 1)

TiO₂ and TiN_xO_y thin films grown by low pressure metal-organic chemical vapor deposition (LP-MOCVD) on top of Si(0 0 1) substrate were characterized by X-ray multiple diffraction. X-ray reflectivity analysis of TiO₂[1 1 0] and TiNO[1 0 0] polycrystalline layers allowed to determine the growth rate (−80 Å/min) of TiO₂ and (−40 Å/min) of TiNO films. X-ray multiple diffraction through the Renninger scans, i.e., ?-scans for (0 0 2)Si substrate primary reflection is used as a non-conventional method to obtain the substrate lattice parameter distortion due to the thin film conventional deposition, from where the information on film strain type is obtained.     

Effects of seed layer on the structure and property of zinc oxide thin films electrochemically deposited on ITO-coated glass

ZnO films with different morphologies were deposited on the ITO-coated glass substrate from zinc nitrate aqueous solution at 65 °C by a seed-layer assisted electrochemical deposition route. The seed layers were pre-deposited galvanostatically at different current densities (i_sl) ranging from −1.30 to −3.0 mA/cm², and the subsequent ZnO films had been done using the potentiostatic technique at the cathode potential of −1.0 V. Densities of nucleation centers in the seed layers varied with increasing the current density, and the ZnO films on them showed variable morphologies and optical properties. The uniform and compact nanocrystalline ZnO film with (0 0 2) preferential orientation was obtained on seed layer that was deposited under the current density (i_sl) of −1.68 mA/cm², which exhibited good optical performances.     

Room-temperature ferromagnetism in Sn1−xMnxO2 nanocrystalline thin films prepared by ultrasonic spray pyrolysis

Sn_1−xMn_xO₂ (x=0.01-0.05) thin films were synthesized on quartz substrate using an inexpensive ultrasonic spray pyrolysis technique. The influence of doping concentration and substrate temperature on structural and magnetic properties of Sn_1−xMn_xO₂ thin films was systematically investigated. X-ray diffraction (XRD) studies of these films reflect that the Mn³⁺ ions have substituted Sn⁴⁺ ions without changing the tetragonal rutile structure of pure SnO₂. A linear increase in c-axis lattice constant has been observed with corresponding increase in Mn concentration. No impurity phase was detected in XRD patterns even after doping 5 at% of Mn. A systematic change in magnetic behavior from ferromagnetic to paramagnetic was observed with increase in substrate temperature from 500 to 700 °C for Sn_1−xMn_xO₂ (x=0.01) films. Magnetic studies reveal room-temperature ferromagnetism (RTFM) with 3.61×10⁻⁴ emu saturation magnetization and 92 Oe coercivity in case of Sn_1−xMn_xO₂ (x=0.01) films deposited at 500 °C. However, paramagnetic behavior was observed for the films deposited at a higher substrate temperature of 700 °C. The presence of room-temperature ferromagnetism in these films was observed to have an intrinsic origin and could be obtained by controlling the substrate temperature and Mn doping concentration.     

Hf1−xSixOy dielectric films deposited by UV-photo-induced chemical vapour deposition (UV-CVD)

Hf_1−xSi_xO_y is an attractive candidate material for high-k dielectrics. We report in this work the deposition of ultra-thin Hf_1−xSi_xO_y films (0.1 ≤ x ≥ 0.6) on silicon substrate at 450 °C by UV-photo-induced chemical vapour deposition (UV-CVD) using 222 nm excimer lamps. Silicon(IV) and hafnium(IV) organic compounds were used as the precursors. Films from around 5 to 40 nm in thickness with refractive indices from 1.782 to 1.870 were grown. The deposition rate was found to be of 6 nm/min at a temperature of 450 °C. The physical, interfacial and electrical properties of hafnium silicate (Hf_1−xSi_xO_y) thin films were investigated by using X-ray photoelectron spectroscopy, ellipsometry, FT-IR, C-V and I-V measurements. XRD showed that they were basically amorphous, while Fourier transform infrared spectroscopy (FT-IR), clearly revealed Hf-O-Si absorption in the photo-CVD deposited Hf_1−xSi_xO_y films. Surface and interfacial properties were analysed by TEM and XPS. It is found that carbon content in the films deposited by UV-CVD is very low and it also decreases with increasing Si/(Si + Hf) ratio, as low as about 1 at.% at the Si/(Si + Hf) ratio of 60 at.%.     

Influence of the substrate material on the properties of pulsed laser deposited thin Li1+xMn2O4−δ films

Thin Li_1+xMn₂O_4−δ films were deposited on several substrate materials (stainless steel, p-doped silicon and glassy carbon) by pulsed laser deposition. To obtain the correct thin film stoichiometries, targets with a different amount of excess lithium were required (Li_1.03Mn₂O₄ + xLi₂O; x = 2.5 and 7.5 mol%). The resulting polycrystalline thin films were characterized with respect to their morphology and electrochemical activity. It was found that only thin Li_1+xMn₂O_4−δ films deposited on stainless steel and glassy carbon showed the typical insertion and deinsertion peaks of Li⁺ during cycling.     

Characterization of Y2O3 gate dielectric on n-GaAs substrates

Physical and electrical properties of sputtered deposited Y₂O₃ films on NH₄OH treated n-GaAs substrate are investigated. The as-deposited films and interfacial layer formation have been analyzed by using X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectroscopy (SIMS). It is found that directly deposited Y₂O₃ on n-GaAs exhibits excellent electrical properties with low frequency dispersion (<5%), hysteresis voltage (0.24 V), and interface trap density (3 × 10¹² eV⁻¹ cm⁻²). The results show that the deposition of Y₂O₃ on n-GaAs can be an effective way to improve the interface quality by the suppression on native oxides formation, especially arsenic oxide which causes Fermi level pinning at high-k/GaAs interface. The Al/Y₂O₃/n-GaAs stack with an equivalent oxide thickness (EOT) of 2.1 nm shows a leakage current density of 3.6 × 10⁻⁶ A cm⁻² at a V_FB of 1 V. While the low-field leakage current conduction mechanism has been found to be dominated by the Schottky emission, Poole-Frenkel emission takes over at high electric fields. The energy band alignment of Y₂O₃ films on n-GaAs substrate is extracted from detailed XPS measurements. The valence and conduction band offsets at Y₂O₃/n-GaAs interfaces are found to be 2.14 and 2.21 eV, respectively.     

Enhanced ferroelectric properties of (Pb0.90La0.10)Ti0.975O3 multilayered thin films prepared by RF magnetron sputtering

The (Pb_0.90La_0.10)Ti_0.975O₃/PbTiO₃ (PLT/PT), PbTiO₃/(Pb_0.90La_0.10)Ti_0.975O₃/PbTiO₃ (PT/PLT/PT) multilayered thin films with a PbO_x buffer layer were in situ deposited by RF magnetron sputtering at the substrate temperature of 600 °C. With this method, highly (1 0 0)-oriented PLT/PT and PT/PLT/PT multilayered thin films were obtained. The PbO_x buffer layer leads to the (1 0 0) orientation of the films. The dielectric, ferroelectric and pyroelectric properties of the PLT multilayered thin films were investigated. It is found that highly (1 0 0)-oriented PT/PLT/PT multilayered thin films possess higher remnant polarization 2P_r (44.1 μC/cm²) and better pyroelectric coefficient at room temperature p (p = 2.425 × 10⁻⁸ C/cm² K) than these of PLT and PLT/PT thin films. These results indicate that the design of the PT/PLT/PT multilayered thin films with a PbO_x buffer layer should be an effective way to enhance the dielectric, ferroelectric and pyroelectric properties. The mechanism of the enhanced ferroelectric properties was also discussed.     

Analysis of the Ge1−xCx films deposited by MFMST

Ge_1−xC_x films deposited by using a medium frequency magnetron sputtering technique (MFMST) were analyzed with X-ray photoelectron and Raman spectroscopy. The deposited Ge_1−xC_x films consist of C, Ge, GeC and GeO_y. The GeC content in the Ge_1−xC_x films linearly decreases, and the C content linearly increases with increasing deposition temperature from 150 to 350 °C. The GeC content decreases from 11.6% at a substrate bias of 250 V to a lowest value of 9.6% at 350 V, then increases again to 10.4% at 450 V. While the C content increases from 49.0% at the bias of 250 V to a largest value of 58.0% at 350 V and then maintains this level at 450 V. It is found that selecting a bias parameter seems more effective than deposition temperature if we want to obtain a higher content of GeC in the deposited films. In addition, a new method is presented in this paper to estimate the changes of GeC content in the Ge_1−xC_x films by observing the shifts of Ge-Ge LO phonon peak in Raman spectra for the Ge_1−xC_x films. The related mechanism is also discussed in this paper.     

White organic electroluminescent device with photovoltaic performances

Organic device with structure of indium tin oxide (ITO)/1,3,5-tris-(3-methylphenylphenylamino)triphenylamine (m-MTDATA)/2-tert-butyl-9,10-di-beta-naphthylanthracene (TBADN)/2,9-dimethyl-4,7-diphenyl-1,10-phenan-throline (BCP)/LiF/Al, was fabricated, which show high efficient white electroluminescence (EL) or photovoltaic (PV) properties when it was driven by direct current (DC) bias or illuminated by ultraviolet (UV) light. Under a DC bias, the device shows efficient white EL emission. A maximum luminous efficiency of 1.1 lm/W was obtained at 8 V, which corresponds the Commission International de L’Eclairage coordinates (CIE) of (x = 0.298, y = 0.365). When the bias was increased to 12 V, the device shows bright white emission with the maximum brightness of 4300 cd/m², corresponding CIE coordinates of (x = 0.262, y = 0.280). When the diode was irradiated by a 365 nm UV-light (4 mW/cm²), the open-circuit voltage (V_oc) of 1.2 V, short-circuit (I_sc) of 0.065 mA/cm², fill factor (FF) of 0.24 and power conversion efficiency of 0.47% have been determined, respectively. The generation mechanisms of white light and PV of the bi-functional diode were discussed as well.     

The effects of Si3N4 interlayer on the thermal stability and hardness of Ti/TiNx (x = 0.5-1) nanolayered coatings

The polycrystalline Ti/TiN_x multilayer films were deposited by magnetron sputtering, and the as-deposited multilayer coatings were annealed at 500-800 °C for 2-4 h in vacuum. We investigated the effects of annealing temperature and annealing time on the microstructural, interfacial, and mechanical properties of the polycrystalline Ti/TiN_x multilayer films. It was found that the hardness increased with annealing temperature. This hardness enhancement was probably caused by the preferred crystalline orientation TiN(1 1 1). The X-ray reflectivity measurements showed that the layer structure of the coatings could be maintained after annealing at 500 °C and the addition of the Si₃N₄ interlayer to Ti/TiN_x multilayer could improve the thermal stability to 800 °C.     

Substrate and orientation influence on electrical properties of sputtered La-doped PZT thin films

Pb_1−2y/3La_yZr_xTi_1−xO₃ (PLZT) thin films have been prepared “in situ” by multi-target sputtering on Silicon, LaAlO₃ (LAO) and MgO substrates covered with a Pt bottom electrode. The purpose was to grow tetragonal PLZT films (Zr/Ti = 28/72 with different La contents) on these various substrates and to compare their electrical properties. To this aim, Pt was first deposited on the three different substrates to get (1 1 1)Pt/Si, (1 1 1)Pt/LAO and (2 0 0)Pt/MgO. Then PLZT was deposited in a same run on these three kinds of substrates and the influence of La contents and film orientation on electrical properties was investigated. The La content was varied from y = 0 to y = 32 in order to explore the phase transition between ferroelectric and paraelectric phases as a function of the substrate. For large amount of Lanthanum, relaxor behavior has been observed and studied.     

Structural and electrical transport properties of ZnxFe3−xO4 thin film deposited on Si (1 1 1) by pulsed-laser deposition

Polycrystalline thin films of Fe_3−xZn_xO₄ (x = 0.0, 0.01 and 0.02) were prepared by pulsed-laser deposition technique on Si (1 1 1) substrate. X-ray diffraction studies of parent as well as Zn doped magnetite show the spinel cubic structure of film with (1 1 1) orientation. The order–disorder transition temperature for Fe₃O₄ thin film with thickness of 150 nm are at 123 K (Si). Zn doping leads to enhancement of resistivity by Zn²⁺ substitution originates from a decrease of the carrier concentration, which do not show the Verwey transition. The Raman spectra for parent Fe₃O₄ on Si (1 1 1) substrate shows all Raman active modes for thin films at energies of T_2g¹, T_2g³, T_2g², and A_1g at 193, 304, 531 and 668 cm⁻¹. It is noticed that the frequency positions of the strongest A_1g mode are at 668.3 cm⁻¹, for all parent Fe₃O₄ thin film shifted at lower wave number as 663.7 for Fe_2.98Zn_0.02O₄ thin film on Si (1 1 1) substrate. The integral intensity at 668 cm⁻¹ increased significantly with decreasing doping concentration and highest for the parent sample, which is due to residual stress stored in the surface.     

Effect of UV lamp irradiation during oxidation of Zr/Pt/Si structure on electrical properties of Pt/ZrO2/Pt/Si structure

Metal-insulator-metal (MIM) capacitors were fabricated using ZrO₂ films and the effects of structural and native defects of the ZrO₂ films on the electrical and dielectric properties were investigated. For preparing ZrO₂ films, Zr films were deposited on Pt/Si substrates by ion beam deposition (IBD) system with/without substrate bias voltages and oxidized at 200 °C for 60 min under 0.1 MPa O₂ atmosphere with/without UV light irradiation (λ = 193 nm, Deep UV lamp). The ZrO₂(∼12 nm) films on Pt(∼100 nm)/Si were characterized by X-ray diffraction pattern (XRD), field emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HRTEM), capacitance-voltage (C-V) and current-voltage (I-V) measurements were carried out on MIM structures. ZrO₂ films, fabricated by oxidizing the Zr film deposited with substrate bias voltage under UV light irradiation, show the highest capacitance (784 pF) and the lowest leakage current density. The active oxygen species formed by UV irradiation are considered to play an important role in the reduction of the leakage current density, because they can reduce the density of oxygen vacancies.