The origin of electrical property deterioration with increasing Mg concentration in ZnMgO:Ga

Transparent conductive Ga-doped Zn_1 − xMg_xO (ZnMgO:Ga) films were epitaxially grown via Pulsed Laser Deposition on sapphire by optimizing the substrate temperature and other parameters of deposition. Zn_0.68Mg_0.31Ga_0.01O/sapphire films deposited at 400 °C have a Hall mobility (μ) of 9.2 ± 0.5 cm² V^− 1 s^− 1 and a free electron density (n) of 1.79 × 10²⁰ ± 0.06 × 10²⁰ cm^− 3, yielding an electrical conductivity (σ) = 262 ± 22 S/cm. Zn_0.90Mg_0.09Ga_0.01O/sapphire films, deposited under the same growth conditions, have similar crystalline quality, but significantly better electrical properties (σ = 1450 ± 10 S/cm, μ = 24.5 ± 2.5 cm² V^− 1 s^− 1, n = 3.81 × 10²⁰ ± 0.20 × 10²⁰ cm^− 3). This comparison provides evidence of electrical property deterioration in doped ZnMgO bulk material with increasing Mg content, independent of crystalline quality. Electrical properties of ZnMgO:Ga are further deteriorated by the decrease of the crystalline quality. Polycrystalline Zn_0.90Mg_0.09Ga_0.01O/a-SiO₂ samples deposited under identical conditions on amorphous silica substrates had both inferior crystal quality and inferior transport properties (μ = 2.5 ± 0.2 cm² V^− 1 s^− 1, n = 2.04 × 10²⁰ ± 0.20 × 10²⁰ cm^− 3, σ = 80 ± 8 S/cm) compared to their epitaxial counterparts. Overall, the results of this study indicate that both bulk material properties and crystalline quality influence the electrical properties of single-phase ZnMgO:Ga thin films.     

Protonic conduction in Ca-doped La2M2O7 (M = Ce, Zr) with its application to ammonia synthesis electrochemically

Complex oxides La_1.95Ca_0.05M₂O_7−δ (M = Ce, Zr) were prepared by sol-gel method and characterized by thermal analysis (TG-DTA), X-ray diffraction (XRD). On the sintered complex oxides as solid electrolyte, the conductivity was measured in various atmospheres, and ammonia was synthesized from nitrogen and hydrogen at atmospheric pressure in the solid states proton conducting cell reactor by electrochemical methods. The rates of ammonia formation were up to 2.0 × 10⁻⁹ mol s⁻¹ cm⁻² for La_1.95Ca_0.05Zr₂O_7−δ and 1.3 × 10⁻⁹ mol s⁻¹ cm⁻² for La_1.95Ca_0.05Ce₂O_7−δ, respectively, at 520 °C.     

An investigation on palladium sulphide (PdS) thin films as a photovoltaic material

Polycrystalline PdS thin films with tetragonal structure have been grown by direct sulphuration of Pd layers. They are formed by crystallites of size ∼ 50 nm. As-grown PdS films show a Seebeck coefficient, S = − 250 ± 30 μV/K, which indicates an n-type conductivity. Electrical resistivity of the samples, measured by the four contact probe, is (6.0 ± 0.6) × 10^− 2 Ω·cm. Hall effect measurements, confirms n-type conductivity with a negative carrier density n = (8.0 ± 2.0) × 10¹⁸ cm^− 3 and electron mobility μ of (20 ± 2) cm²/V s. Band gap energy (E_g) and absorption coefficient (α) are determined from the optical transmission and reflectance of the films. A direct transition with energy gap E_g = (1.60 ± 0.01) eV is obtained. Optical absorption coefficient in the range of photon energies hν > 2.0 eV is higher than 10⁵ cm^− 1. All these properties make PdS thin films a good alternative material for solar applications.     

The electrical measurements in poly(2-chloroaniline) based thin film sandwich devices

Al/P2ClAn(CH₃COOH)/p-Si/Al structure has been obtained by evaporation of the polymer P2ClAn(CH₃COOH) on the front surface of p-type silicon substrate, P2ClAn: the poly(2-chloroaniline). The P2ClAn emeraldine salt was chemically synthesized by using acetic acid (CH₃COOH). It has been seen that the current-voltage characteristics of the heterojunction obey to space charge-limited current model. Furthermore, P2ClAn(CH₃COOH) was characterized by using Fourier Transform Infrared (FTIR) and Ultraviolet-Visible (UV-Vis) spectroscopies. An average value of μ, 2.43 × 10^− 5 cm² V^− 1 s^− 1, was obtained for the mobility of the P2ClAn(CH₃COOH); this value is in agreement with the value of about 10^− 4 cm² V^− 1 s^− 1 given for the conjugated polymeric thin films in the literature. Low capacitance-voltage-frequency and conductance-frequency measurements have been made at the voltages of 0.00, 0.02 and 0.30 V in the frequency range of 100 Hz-2.0 MHz. An average value of 7.91 × 10¹¹ cm^− 2 eV^− 1 for interface state density has been obtained from the frequency-capacitance characteristics.     

Chemical diffusion coefficient of lithium ion in Li3V2(PO4)3 cathode material

The kinetic properties of monoclinic lithium vanadium phosphate were investigated by potential step chronoamperometry (PSCA) and electrochemical impedance spectroscopy (EIS) method. The PSCA results show that there exists a linear relationship between the current and the square root of the time. The D?_Li values of lithium ion in Li_3-xV₂(PO₄)₃ under various initial potentials of 3.41, 3.67, 3.91 and 4.07 V (vs Li/Li⁺) obtained from PSCA are 1.26 × 10^− 9, 2.38 × 10^− 9, 2.27 × 10^− 9 and 2.22 × 10^− 9 cm²·s^− 1, respectively. Over the measuring temperature range 15-65 °C, the diffusion coefficient increased from 2.67 × 10^− 8 cm²·s^− 1 (at 15 °C) to 1.80 × 10^− 7 cm²·s^− 1 (at 65 °C) as the measuring temperature increased.     

Growth and spectral properties of Cr:KAl(MoO4)2 crystal

The Cr³⁺:KAl(MoO₄)₂ single crystal was grown by top seeding solution growth method (TSSG). Based on the absorption and emission spectra, the crystal field strength Dq, the Racah parameters B and C, the effective phonon energy ?ω and the Huang-Rhys factor S were calculated: Dq = 1494.8 cm^− 1, B = 585.5 cm^− 1 and C = 3049 cm^− 1, ?ω = 373.8 cm^− 1 and the Huang-Rhys factor S = 3.74, respectively. The value Dq/B = 2.55 indicates that Cr³⁺ ion occupies the strong crystal field site in KAl(MoO₄)₂ crystal. A comparison of crystal field parameters for Cr³⁺:KAl(MoO₄)₂ with other Cr³⁺-doped crystals was presented. The results of spectral measurement show that Cr³⁺:KAl(MoO₄)₂ may be a potential candidate for broadband laser applications.     

Crystal structure, thermal expansion and electrical properties of a new compound Al0.33DyGe2

A new ternary compound Al_0.33DyGe₂ has been synthesized and studied from 298 K to773 K by means of X-ray powder diffraction technique. The crystal structural refinement of Al_0.33DyGe₂ has been performed by using the Rietveld method. The ternary compound Al_0.33DyGe₂ crystallizes in the orthorhombic of the defect CeNiSi₂-type structure (space group Cmcm, a = 0.41018(2)nm, b = 1.62323(6)nm, c = 0.39463(1)nm, Z = 4 and D_calc = 8.004 g/cm³). The average thermal expansion coefficients α_a, α_b and α_c of Al_0.33DyGe₂ are 1.96 × 10^− 5 K^− 1, 0.93 × 10^− 5 K^− 1 and 1.42 × 10^− 5 K^− 1, respectively. The bulk thermal expansion coefficient α_V is 4.31 × 10^− 5 K^− 1. The resistivity is observed to fall from 387 to 308 µΩ cm between room temperature and 25 K.     

Transport characteristics of ZrO2 dispersed mixed (BaCl2)1−x-(KCl)x solid electrolytes

Composite solid electrolytes in the system [(BaCl₂)_1−x:(KCl)_x]_1−y:(ZrO₂)_y were prepared following the conventional ceramic powder processing route. In the mixed matrix system prepared by melt quench technique, a nominal increase in conductivity (σ) was found in (BaCl₂)_0.9:(KCl)_0.1. On ZrO₂ particle dispersion in this mixed matrix, the maximum conductivity (∼90 times that of base matrix value) was found to occur with 50 m/o of ZrO₂. Conductivity increases monotonically over the temperature range from 100 to 300 °C studied and attains the value of 10 × 10⁻⁶ S cm⁻¹ at 300 °C. The mobility (μ) of the charge carriers at room temperature was found to be 18.5 × 10⁻² cm² V⁻¹ s⁻¹ and the increase in μ with temperature was not very significant. The transference ionic number determination showed that the electrical conductivity of the electrolyte is predominantly due to ions. This study indicates that the conductivity is governed by mobile ion concentration.     

Surface mound formation during epitaxial growth of CrN(001)

Single crystal CrN(001) layers, 10 to 160 nm thick, were grown on MgO(001) by reactive magnetron sputtering at growth temperatures T_s = 600 and 800 °C. Insitu scanning tunneling microscopy shows that all layer surfaces exhibit mounds with atomically smooth terraces that are separated by monolayer-high step edges aligned along ( 110) directions, indicating N-rich surface islands. For T_s = 600 °C, the root mean square surface roughness σ initially increases sharply from 0.7 ± 0.2 for a thickness t = 10 nm to 2.4 ± 0.5 nm for t = 20 nm, but then remains constant at σ = 2.43 ± 0.13 nm for t = 40, 80 and 160 nm. The mounds exhibit square shapes with edges along ( 110) directions for t ≤ 40 nm, but develop dendritic shapes at t = 80 nm which revert back to squares at t = 160 nm. This is associated with a lateral mound growth that is followed by coarsening, yielding a decrease in the mound density from 5700 to 700 µm⁻² and an initial increase in the lateral coherence length ξ from 7.2 ± 0.6 to 16.3 ± 0.8 to 24 ± 3 nm for t = 10, 20, and 40 nm, respectively, followed by a drop in ξ to 22 ± 2 and 16 ± 2 nm for t = 80 and 160 nm, respectively. Growth at T_s = 800 °C results in opposite trends: σ and ξ decrease by a factor of 2, from 2.0 ± 0.4 and 20 ± 4 nm for t = 10 nm to 0.92 ± 0.07 and 10.3 ± 0.4 nm for t = 20 nm, respectively, while the mound density remains approximately constant at 900 μm⁻². This unexpected trend is associated with mounds that elongate and join along ( 100) directions, yielding long chains of interconnected square mounds for t = 40 nm. However, coalescence during continued growth to t = 160 nm reduces the mound density to 100 µm⁻² and increases σ and ξ to 2.5 ± 0.1 and 40 ± 2 nm, respectively.     

Growth and properties of Ca0.28Ba0.72Nb2O6 single crystals

Calcium barium niobate Ca_0.28Ba_0.72Nb₂O₆ (CBN-28) crystals were successfully grown by the Czochralski method. X-ray powder diffraction experiments indicated that CBN single crystals are tetragonal with a = 12.432(±0.002) Å and c = 3.957(±0.001) Å, which have almost the same structure as the Sr_0.50Ba_0.50Nb₂O₆ (SBN-50) crystal. The thermal expansion coefficient perpendicular to Z-direction had been measured to be 1.25 × 10⁻⁵ K⁻¹ between 293.15 and 572.15 K, and along Z-axis was negative between 298.15 and 543.15 K. The specific heat of the crystal had been measured by the differential scanning calorimetric experiments. The transmittance spectra from 200 to 3200 nm were also measured. The measured temperature dependence of dielectric constants showed that the Curie temperature of the CBN-28 crystals is 260 °C, which is about 200 °C higher than that of the (SBN) crystal.     

Microhardness studies on calcium hydrogen phosphate (brushite) crystals

Vicker's and Knoop microhardness studies were carried out on grown calcium hydrogen phosphate dihydrate (CaHPO₄·2H₂O) crystals over a load range of 10-50 g. The Vickers (H_V) and Knoop (H_K) microhardness numbers for the above loads were found to be in the range of 94-170 kg/mm² and 28-35 kg/mm² respectively. It was also found that these numbers increased with increase in load. The Mayer's index (n) was found to be greater than 1.6 showing soft-material characteristics. The fracture toughness values (K_c), determined from measurements of crack length, were estimated to be 6 ± 0.5 × 10³ kg m^−3/2 and 4.5 ± 0.5 × 10³ kg m^−3/2 at 25 g and 50 g respectively. The brittleness indices (B_i) were found as 2.3 ± 0.1 × 10⁴ m^−1/2 for 25 g and 3.7 ± 0.1 × 10⁴ m^−1/2 for 50 g. Using Wooster's empirical relation, the elastic stiffness coefficient (c₁₁) has been calculated from Vicker's hardness values as 4.8 ± 0.5 × 10¹⁵ Pa for 10 g, 9.7 ± 0.5 × 10¹⁵ Pa for 25 g and 13.3 ± 0.5 × 10¹⁵ Pa for 50 g. The Young's modulus was calculated as 1.5 ± 0.1 × 10¹⁰ N m⁻² from Knoop microhardness values.     

Pseudo spin-valves with different spacer thickness as sensing elements of mechanical strain

Giant magnetoresistance (GMR) effect in cobalt based pseudo spin-valves (SV) is combined with the inverse magnetostriction in sensors of mechanical strain. SV with Co/Au/Co core structure were deposited onto the flexible 125 μm thick polyimide substrates. The influence of magnetostriction on GMR was studied in bending current-in-plane configuration. Total relative strain was between −8.6 × 10⁻³ (compression) and 8.6 × 10⁻³ (tension). SV were designed with respect to the oscillating nature of exchange coupling force vs. spacer thickness. The period of oscillations is not changing under the applied stress in our experimental configuration. From the magnetoresistance ratio vs. strain dependences it follows that the output signal of the strained sensor vs. unloaded one could be improved by a proper choice of the spacer thickness t_s. If t_s = 4 nm the relative output is 36% and for t_s = 2.4 nm it is 34%, however, in this case only in the half range of the strain between 0 and ±8.6 × 10⁻³. For t_s = 2.2 nm the relative output is only 10%.     

Effect of environmental humidity on rate of thermal outgassing

This investigation presents a super-dry venting system that allows the rate of thermal outgassing of an aluminum chamber (length 2 m) to return rapidly to 1 × 10⁻¹³ mbar L s⁻¹ cm⁻² in 4 h without baking. A glove box and an air shower, which provided dehumidified environments with water vapor concentrations of 0.1 ppm and 5 ppm respectively, were utilized to assess the effect of environmental humidity on the rate of thermal outgassing. With super-dry nitrogen venting inside and exposure to the glove box, a thermal outgassing rate of q₁ ∼ 1 × 10⁻¹¹ mbar L s⁻¹ cm⁻² was achieved.     

Kapitza resistance and thermal conductivity of Mylar at superfluid helium temperature

The Kapitza resistance and the thermal conductivity of type A Mylar sheets in the temperature range between 1.4 and 2.1 K have been determined. Four sheets with varying thickness from 37 μm to 255 μm, have been tested in steady-state condition. For a small temperature difference (10-30 mK) and heat flux density smaller than 30 Wm⁻², the total thermal resistance of the sheet is determined as a function of sheet thickness and bath temperature. The Kapitza resistance is given by R_K = (1.28 ± 0.08)T⁻³ × 10⁻³ Km² W⁻¹, and the thermal conductivity, κ = [(8.83 ± 0.75) + (11.73 ± 0.43) × T] × 10⁻³ Wm⁻¹ K⁻¹.     

Crystal structure and ionic conductivity of ruthenium diphosphate ARu2(P2O7)2, A=Li, Na, and Ag, with a tunnel structure

Crystal structure and ionic conductivity of ruthenium diphosphates, ARu₂(P₂O₇)₂ A=Li, Na, and Ag, were investigated. The structure of the Ag compound was determined by single crystal X-ray diffraction techniques. It crystallized in the triclinic space group P−1 with a=4.759(2) Å, b=6.843(2) Å, c=8.063(1) Å, α=90.44(2)°, β=92.80(2)°, γ=104.88(2)°, V=253.4(1) Å³. The host structure of it was composed of RuO₆ and P₂O₇ groups and formed tunnels running along the a-axis, in which Ag⁺ ions were situated. The ionic conductivities have been measured on pellets of the polycrystalline powders. The Li and Ag compounds showed the conductivities of 1.0×10⁻⁴ and 3.5×10⁻⁵ S cm⁻¹ at 150 °C, respectively. Magnetic susceptibility measurement of the Ag compound showed that it did not obey the Curie-Weiss law and the effective magnetic moment decreased as temperature decreased due to the large spin-orbital coupling effect of Ru⁴⁺ ions.     

Synthesis and characteristics of the C12A7-O nanoparticles by citric acid sol-gel combustion method

In this study, the O⁻-containing nanocrystal 12CaO·7Al₂O₃ (C12A7-O⁻) was synthesized by the citric acid sol-gel combustion method. The formation of the C12A7-O⁻ material was investigated via X-ray diffraction, thermogravimetric analysis, differential thermal analysis, electron paramagnetic resonance, field emission-scanning electron microscopy, and time of flight mass spectroscopy. The C12A7-O⁻ material was formed at a lower synthesis temperature (900-1150 °C), with a narrower particle size (33-74 nm). The anionic species stored in the C12A7 material was dominated by the active atomic oxygen anions (O⁻) with a concentration of (1.2 ± 0.3) × 10²⁰ cm^− 3, and the emission current density of O⁻ was about 0.89 ± 0.15 μA/cm² at T_{(sample surface)} = 800 °C and E_{(extraction field)} = 800 V/cm.     

Copper phthalocyanine thin-film field-effect transistor with SiO2/Ta2O5/SiO2 multilayer insulator

Top-contact Copper phthalocyanine (CuPc) thin-film field-effect transistor (TFT) with SiO₂/Ta₂O₅/SiO₂ (STS) multilayer as the dielectric was fabricated and investigated. With the multi-layer dielectric, drive voltage was remarkably reduced. A relatively large on-current of 1.1 × 10⁻⁷ A at a V_GS of −15 V was obtained due to the strong coupling capability provided by the STS multilayer gate insulator. The device shows a moderate performance: saturation mobility of μ_sat = 6.12 × 10⁻⁴ cm²/V s, on-current to off-current ratio of I_on/I_off = 1.1 × 10³, threshold voltage of V_TH = −3.2 V and sub-threshold swing SS = 1.6 V/dec. Atomic force microscope images show that the STS multilayer has a relative smooth surface. Experiment results indicate that STS multilayer is a promising insulator for the low drive voltage CuPc-based TFTs.     

Growth and electrical properties of mercury indium telluride single crystals

A novel photoelectronic single crystal, mercury indium telluride (MIT), has been successfully grown by using vertical Bridgman method (VB). The crystallinity, thermal and electrical properties of the MIT crystal were investigated. The results of X-ray rocking curve show that the as-grown MIT crystal has good crystal quality with the FWHM on (3 1 1) face of about 173 in. DSC measurement reveals that the Hg element is easy to solely evaporate from the compound when the temperature is higher than 387.9 °C in the open system. Hall measurements at room temperature show that the resistivity, carrier density and mobility of the MIT crystal were 4.79 × 10² Ω cm, 2.83 × 10¹³ cm⁻³ and 4.60 × 10² cm² V⁻¹ s⁻¹, respectively. The reduction of carrier mobility and the increase of the resistivity are related to the adding of In₂Te₃ into HgTe, which changes the energy band structure of the crystal.     

Electrical characterization of high-k gate dielectrics on Ge with HfGeN and GeO2 interlayers

Two kinds of HfSiO_x/interlayers (ILs)/Ge gate stack structures with HfGeN- and GeO₂-ILs were fabricated using electron cyclotron resonance (ECR) plasma sputtering and the subsequent post deposition annealing (PDA). It was found that HfGe was formed by the deposition of Hf metal on Ge and changed to HfGeN by N₂ ECR-plasma irradiation, which was used as IL. Another IL was GeO₂, which was grown by thermal oxidation at 500 °C. For dielectrics with HfGeN-IL, PDA of 550 °C resulted in effective oxide thickness (EOT) of 2.2 nm, hysteresis of 0.1 V, and interface state density (D_it) = 7 × 10¹² cm^− 2 eV^− 1. For dielectrics with GeO₂-IL, PDA of 500 °C resulted in EOT of 2.8 nm, hysteresis of 0.1 V, and D_it = 1 × 10¹² cm^− 2 eV^− 1. The structural change of HfSiO_x/GeO₂/Ge during the PDA was clarified by using X-ray photoelectron spectroscopy, and the gate stack formation for obtaining the good IL was discussed.     

The impact of high-dose implantation into manganin on its thermo-resistance properties under high pressure

Using high-dose implantation into manganin of 253 MeV Kr ions (a surface dose of 2.5×10¹⁵ ion/cm²), as well as 250 keV Bi ions (a surface dose of 10¹⁷ ion/cm²) and 250 keV Kr ions (a surface dose of 10¹⁶ ion/cm²), the pressure and temperature sensitivities of manganin foil have been investigated. It was found that the pressure sensitivity of manganin increased (α=2.45×10⁻⁵ MPa⁻¹ before implantation and α_imp=4.60×10⁻⁵ MPa⁻¹ after complex implantation with 250 keV of Bi and Kr ions, the accuracy of estimation does not exceed 0.01×10⁻⁵ MPa⁻¹) and its temperature sensitivity remained appreciably reduced.