CuInS2 thin films obtained through the annealing of chemically deposited In2S3-CuS thin films

In this work, we report the formation of CuInS₂ thin films on glass substrates by heating chemically deposited multilayers of copper sulfide (CuS) and indium sulfide (In₂S₃) at 300 and 350 °C in nitrogen atmosphere at 10 Torr. CIS thin films were prepared by varying the CuS layer thickness in the multilayers with indium sulfide. The XRD analysis showed that the crystallographic structure of the CuInS₂ (JCPDS 27-0159) is present on the deposited films. From the optical analysis it was estimated the band gap value for the CIS film (1.49 eV). The electrical conductivity varies from 3 × 10⁻⁸ to 3 Ω⁻¹ cm⁻¹ depending on the thickness of the CuS film. CIS films showed p-type conductivity.     

Influence of postdeposition annealing on structural properties and electrical characteristics of thin Tm2O3 and Tm2Ti2O7 dielectrics

We describe the structural properties and electrical characteristics of thin thulium oxide (Tm₂O₃) and thulium titanium oxide (Tm₂Ti₂O₇) as gate dielectrics deposited on silicon substrates through reactive sputtering. The structural and morphological features of these films were explored by X-ray diffraction, X-ray photoelectron spectroscopy, secondary ion mass spectrometry, and atomic force microscopy, measurements. It is found that the Tm₂Ti₂O₇ film annealed at 800 °C exhibited a thinner capacitance equivalent thickness of 19.8 Å, a lower interface trap density of 8.37 × 10¹¹ eV⁻¹ cm⁻², and a smaller hysteresis voltage of ∼4 mV than the other conditions. We attribute this behavior to the Ti incorporated into the Tm₂O₃ film improving the interfacial layer and the surface roughness. This film also shows negligible degrees of charge trapping at high electric field stress.     

Electrical properties of La2O3 thin films grown on TiN/Si substrates via atomic layer deposition

The electrical as well as the structural properties of La₂O₃ thin films on TiN substrates were investigated. Amorphous stoichiometric La₂O₃ thin films were grown at 300 °C via atomic layer deposition technique by using lanthanum 2,2,6,6-tetramethyl-3,5-heptanedione [La(TMHD)₃] and H₂O as precursors. Post-annealing of the grown film induced dramatic changes in structural and the electrical properties. Crystalline phases of the La₂O₃ film emerged with the increase of the post-annealing temperature. Metal-insulator-metal (MIM) capacitor was fabricated to measure the electrical properties of the grown film. The dielectric constant of the La₂O₃ thin films increased with annealing temperature to reach the value of 17.3 at 500 °C. The leakage current density of the film post-annealed at 400 °C was estimated to be 2.78 × 10⁻¹⁰ and 2.1 × 10⁻⁸ A/cm² at ±1 V, respectively.     

Characteristics of Ti0.97Co0.03O2:Sb0.01 dilute magnetic semiconducting thin films deposited at 500 °C by pulsed laser deposition

Epitaxial Ti_0.97Co_0.03O₂:Sb_0.01(TCO:Sb) films were deposited on R-Al₂O₃ (1 1 0 2) substrates at 500 °C in various deposition pressures by pulsed laser deposition. The solubility of cobalt within the films increases with decreasing deposition pressure at a deposition temperature of 500 °C. The TCO:Sb films deposited at 5×10⁻⁶ Torr exhibit a p-type anomalous Hall effect having a hole concentration of 6.1×10²²/cm³ at 300 K. On the other hand, films deposited at 4×10⁻⁴ Torr exhibits an n-type anomalous Hall effect having an electron concentration of about 1.1×10²¹/cm³. p- or n-type DMS characteristics depends on the change of the structure of TCO:Sb films and the solubility of Co is possible by controlling the deposition pressure.     

Influence of substrate temperature on structures and dielectric properties of pyrochlore Bi1.5Zn1.0Nb1.5O7 thin films prepared by pulsed laser deposition

The influence of substrate temperature on structural and dielectric properties of cubic pyrochlore Bi_1.5Zn_1.0Nb_1.5O₇ (BZN) thin films prepared by pulsed laser deposition process has been investigated. BZN thin films were deposited on Pt/Ti/SiO₂/Si(1 0 0) substrate and in situ annealed at 700 °C. The results indicate that the substrate temperature has a significant effect on the structural and dielectric properties of BZN thin films. The films exhibit a cubic pyrochlore structure in the substrate temperature range from 550 °C to 700 °C and at the annealing temperature of 700 °C. With further increase of substrate temperature to 750 °C, the phases of Bi₂O₃, BiNbO₄ and Bi₅Nb₃O₁₅ can be detected in the XRD pattern due to the Zn loss. The dielectric constant and loss tangent of the films deposited at 650 °C are 192 and 6 × 10⁻⁴ at 10 kHz, respectively. The tunability is 10% at a dc bias field of 0.9 MV/cm.     

Stabilization of a very high-k crystalline ZrO2 phase by post deposition annealing of atomic layer deposited ZrO2/La2O3 dielectrics on germanium

The impact of the ZrO₂/La₂O₃ film thickness ratio and the post deposition annealing in the temperature range between 400 °C and 600 °C on the electrical properties of ultrathin ZrO₂/La₂O₃ high-k dielectrics grown by atomic layer deposition on (1 0 0) germanium is investigated. As-deposited stacks have a relative dielectric constant of 24 which is increased to a value of 35 after annealing at 500 °C due to the stabilization of tetragonal/cubic ZrO₂ phases. This effect depends on the absolute thickness of ZrO₂ within the dielectric stack and is limited due to possible interfacial reactions at the oxide/Ge interface. We show that adequate processing leads to very high-k dielectrics with EOT values below 1 nm, leakage current densities in the range of 0.01 A/cm², and interface trap densities in the range of 2-5 × 10¹² eV⁻¹ cm⁻².     

Structural and optical properties of SrCu2O2 films deposited on sapphire substrates by pulsed laser deposition

We deposited SrCu₂O₂ (SCO) films on sapphire (Al₂O₃) (0 0 0 1) substrates by pulsed laser deposition. The crystallographic orientation of the SCO thin film showed clear dependence on the growth temperature. X-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis showed that the film deposited at 400 °C was mainly oriented in the SCO [2 0 0] direction, whereas when the growth temperature was increased to 600 °C, the SCO film showed a dominant orientation of SCO [1 1 2]. The SCO film deposited at 500 °C was obvious polycrystalline, showing multi peaks from (2 0 0), (1 1 2), and (2 1 1) diffraction in the XRD spectrum. The SCO film deposited at 600 °C showed a band gap energy of 3.3 eV and transparency up to 80% around 500 nm. The photoluminescence (PL) spectra of the SCO films grown at 500 °C and 600 °C mainly showed blue-green emission, which was attributed to the intra-band transition of the isolated Cu⁺ and Cu⁺–Cu⁺ pairs according to the temperature dependent-PL analysis.     

Influence of substrate temperature in BiFeO3-CoFe2O4 nanocomposites deposited on SrTiO3 (0 0 1)

BiFeO₃-CoFe₂O₄ epitaxial nanocomposites have been deposited on SrTiO₃ (0 0 1) substrates by pulsed laser deposition. We present here a study of the influence of the deposition temperature (T_S), in the 550-800 °C range, on the film composition, morphology and microstructure. Electron-probe microanalysis shows strong reduction of the Bi content in the films when increasing T_S. Films prepared at T_S=750 °C and above are virtually Bi-free. X-ray diffraction (XRD) data show that, due to the volatility of Bi, there is a progressive reduction in the amount of BiFeO₃. The deposition temperature and the concomitant presence of Fe_xO_y spurious phases in the nanocomposites grown at high temperature promote radical changes in film morphology and magnetization. It thus follows that a temperature range suitable for controlled modification of nanocomposites morphology would be extremely narrow.     

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.     

The ν1 + 3ν2 + 3ν3 and 4ν1 + ν2 + ν3 bands of ozone by CW-cavity ring down spectroscopy between 5900 and 5960 cm

The absorption spectrum of ozone, ¹⁶O₃, has been recorded in the 5903-5960 cm⁻¹ region by high sensitivity CW-cavity ring down spectroscopy (α_min ∼ 5 × 10⁻¹⁰ cm⁻¹). The ν₁ + 3ν₂ + 3ν₃ and 4ν₁ + ν₂ + ν₃ A-type bands centred at 5919.15 and 5947.07 cm⁻¹ were newly observed. A set of 173 and 168 energy levels could be experimentally determined for the (1 3 3) and (4 1 1) states, respectively. Except for a few K_a = 5 levels of the (4 1 1) state, the rotational structure of the two states was found mostly unperturbed. The spectroscopic parameters were determined from a fit of the corresponding line positions by considering the (1 3 3) and (4 1 1) states as isolated. The determined effective Hamiltonian and transition moment operators were used to generate a list of 785 transitions given as Supplementary Material.     

Effect of crystallinity of Co layer on perpendicular exchange bias in Au-capped ultrathin Co film on Cr2O3(0 0 0 1) thin film

The effect of the crystalline quality of ultrathin Co films on perpendicular exchange bias (PEB) has been investigated using a Au/Co/Au/α-Cr₂O₃ thin film grown on a Ag-buffered Si(1 1 1) substrate. Our investigation is based on the effect of the Au spacer layer on the crystalline quality of the Co layer and the resultant changes in PEB. An α-Cr₂O₃(0 0 0 1)layer is fabricated by the thermal oxidization of a Cr(1 1 0) thin film. The structural properties of the α-Cr₂O₃(0 0 0 1) layer including the cross-sectional structure, lattice parameters, and valence state have been investigated. The fabricated α-Cr₂O₃(0 0 0 1) layer contains twin domains and has slightly smaller lattice parametersthan those of bulk-Cr₂O₃. The valence state of the Cr₂O₃(0 0 0 1) layer is similar to that of bulk Cr₂O₃. The ultrathin Co film directly grown on the α-Cr₂O₃(0 0 0 1) deposited by an e-beam evaporator is polycrystalline. The insertion of a Au spacer layer with a thickness below 0.5 nm improves the crystalline quality of Co, probably resulting in hcp-Co(0 0 0 1). Perpendicular magnetic anisotropy (PMA) appears below the Néel temperature of Cr₂O₃ for all the investigated films. Although the PMA appears independently of the crystallinequality of Co, PEB is affected by the crystalline quality of Co. For the polycrystalline Co film, PEB is low, however, a high PEB is observed for the Co films whose in-plane atom arrangement is identical to that of Cr³⁺ in Cr₂O₃(0 0 0 1). The results are qualitatively discussed on the basis of the direct exchange coupling between Cr and Co at the interface as the dominant coupling mechanism.     

Electrical properties vs. microstructure of nanocrystallized V2O5-P2O5 glasses — An extended temperature range study

An electronically conducting nanomaterial was synthesized by nanocrystallization of a 90V₂O₅·10P₂O₅ glass and its electrical properties were studied in an extended temperature range from − 170 to + 400 °C. The conductivity of the prepared nanomaterial reaches 2 ? 10^− 1 S cm^− 1 at 400 °C and 2 ? 10^− 3 S cm^− 1 at room temperature. It is higher than that of the original glass by a factor of 25 at room temperature and more than 100 below − 80 °C. A key role in the conductivity enhancement was ascribed to the material's microstructure, and in particular to the presence of the large number of small (ca. 20 nm) grains of crystalline V₂O₅. The observed conductivity dependencies are discussed in terms of the Mott's theory of the electronic hopping transport in disordered systems. Since V₂O₅ is known for its ability to intercalate lithium, the presented results might be helpful in the development of cathode materials for Li-ion batteries.     

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.     

Optical properties of In2O3 oxidized from InN deposited by reactive magnetron sputtering

Unintentionally doped and zinc-doped indium nitride (U-InN and InN:Zn) films were deposited on (0 0 0 1) sapphire substrates by radio-frequency reactive magnetron sputtering, and all samples were then treated by annealing to form In₂O₃ films. U-InN and InN:Zn films have similar photon absorption characteristics. The as-deposited U-InN and InN:Zn film show the absorption edge, ∼1.8-1.9 eV. After the annealing process at 500 °C for 20 min, the absorption coefficient at the visible range apparently decreases, and the absorption edge is about 3.5 eV. Two emission peaks at 3.342 eV (371 nm) and 3.238 eV (383 nm) in the 20 K photoluminescence (PL) spectrum of In₂O₃:Zn films were identified as the free-exciton (FE) or the near band-to-band (B-B) and conduction-band-to-acceptor (C-A) recombination, respectively.     

Solid-state synthesis and magnetic properties of epitaxial FePd3(0 0 1) films

The solid-state synthesis of magnetically soft phase FePd₃ in epitaxial Pd(0 0 1)/Fe(0 0 1)/MgO(0 0 1) film systems was studied experimentally. The system had a Fe to Pd ratio of 1:3. An increase to 450 °C leads to the formation of three variants of ordered L1₀-FePd crystallites. At 500 °C, the solid-state reaction of unreacted Pd with L1₀-FePd crystallites initiates the growth of an ordered epitaxial L1₂-FePd₃(0 0 1) layer. When annealing at 650 °С, a gradual disordering is observed. The magnetic anisotropy (K₁=−2.0×10³ erg/cm³) and the saturation magnetization (M_S=650 emu/cm³) of the disordered FePd₃ phase were determined.     

Preparation and characterization of Cu(In,Ga)(Se,S)2 films without selenization by co-sputtering from Cu(In,Ga)Se2 quaternary and In2S3 targets

In this study, Cu(In,Ga)(Se,S)₂ (CIGSS) thin films were deposited onto a bi-layer Mo coated soda-lime glass by co-sputtering a chalcopyrite Cu(In,Ga)Se₂ (CIGS) quaternary alloy target and an In₂S₃ binary target. A one-stage annealing process was performed to form CIGSS chalcopyrite phase without post-selenization. Experimental results show that CIGSS films were prepared by the proposed co-sputter process via CIGS (70 W by radio frequency) and In₂S₃ (30 W by direct current) with a substrate temperature of 373 K, working pressure of 0.67 Pa, and one-stage annealing at 798 K for 30 min. The stoichiometry ratios of the CIGSS film were Cu/(In + Ga) = 0.92, Ga/(In + Ga) = 0.26, and Se/(S) = 0.49 that approached device-quality stoichiometry ratio (Cu/(In + Ga) < 0.95, Ga/(In + Ga) < 0.3, and (Se/S) ≈ 0.5). The resistivity of the sample was 14.8 Ω cm, with a carrier concentration of 3.4 × 10¹⁷ cm⁻³ and mobility of 1.2 cm² V⁻¹ s⁻¹. The resulting film exhibited p-type conductivity with a double graded band-gap structure.     

The investigation of room temperature ferromagnetism in (1 0 0) oriented BaNb2O6 PLD films on LaAlO3 (1 0 0) substrate

(1 0 0) oriented BaNb₂O₆ films have been successfully grown on LaAlO₃ (1 0 0) substrate at 750 °C or 450 °C in vacuum by pulsed laser deposition. The deposited BaNb₂O₆ PLD films exhibit room-temperature ferromagnetism. Ab initio calculations demonstrate that stoichiometric BaNb₂O₆ and that with barium vacancy are nonmagnetic, while oxygen and niobium vacancy can induce magnetism due to the spin-polarization of Nb s electrons and O p electrons respectively. Moreover, ferromagnetic coupling is energetically more favorable when two Nb/O vacancies are located third-nearest-neighbored. The observed room temperature ferromagnetism in BaNb₂O₆ films should be mainly induced by oxygen vacancies introduced during vacuum deposition, with certain contribution by Nb vacancies.     

Crystallization of 21.25Gd2O3-63.75MoO3-15B2O3 glass induced by femtosecond laser at the repetition rate of 250 kHz

We report the formation of β′-Gd₂(MoO₄)₃ (GMO) crystal on the surface of the 21.25Gd₂O₃-63.75MoO₃-15B₂O₃ glass, induced by 250 kHz, 800 nm femtosecond laser irradiation. The morphology of the modified region in the glass was clearly examined by scanning electron microscopy (SEM). By micro-Raman spectra, the laser-induced crystals were confirmed to be GMO phases and it is found that these crystals have a strong dependence on the number and power of the femtosecond laser pulses. When the irradiation laser power was 900 mW, not only the Raman peaks of GMO crystals but also some new peaks at 214 cm⁻¹, 240 cm⁻¹, 466 cm⁻¹, 664 cm⁻¹ and 994 cm⁻¹which belong to the MoO₃ crystals were observed. The possible mechanisms are proposed to explain these phenomena.     

Structural characterization of La0.9Ba0.1MnO3/Y-ZrO2 film by X-ray diffraction

Perovskite manganite La_0.9Ba_0.1MnO₃(LBMO) films were deposited on (0 0 1)-oriented single crystal yttria-stabilized zirconia (YSZ) substrate by 90° off-axis radio frequency magnetron sputtering. The film thickness ranged from 10 nm to 100 nm. Grazing incidence X-ray diffraction technique and high resolution X-ray diffraction were applied to characterize the structure of LBMO films. The LBMO film mainly consisted of (0 0 1)-orientated grain as well as weakly textured (1 1 0)-orientated grain. The results indicated that an amorphous layer with thickness of about 4 nm was formed at the LBMO/YSZ interface. The strain in LBMO film was small and averaged to be about -0.14%. The strain in the film was not lattice mismatch-induced strain but residual strain due to the difference in thermal expansion coefficient between film and substrate.     

Electrochemical behaviour of sputtered c-V2O5 and LiCoO2 thin films for solid state lithium microbatteries

Here are reported for the first time electrochemical data on all-solid-state lithium microbatteries using crystalline sputtered V₂O₅ thin films as cathode materials and LiPON as solid electrolyte. The stable specific capacity of 30 µAh/cm² found with a 2.4 µm thick film competes very well with the best values obtained for solid state microbatteries using amorphous films. With the challenge of decreasing the temperature of heat treatment for sputtered LiCoO₂ thin films, we show that a temperature of 500 °C combined with an optimized bias sputtering (-50 V) allows to get highly crystalline deposits, to minimize the presence of Co₃O₄ and to suppress any trace of the cubic phase. At the same time the theoretical specific capacity is reached in the 4.2 V-3 V range and a good cycling behaviour is achieved with a high capacity of 50 µAh/cm²/µm after 140 cycles at 10 µA.cm².