Photoelectrochemical properties of brush plated Cd x Zn1−x Se films

Cd _x Zn_1−x Se films(0 ≤ x ≤ 1) were deposited for the first time by the brushplating technique at room temperature from an aqueous bath containing zincsulphate, cadmium sulphate and selenium oxide. The deposition current densitywas varied in the range of 50–250 mA cm⁻². The as deposited films exhibitedcubic structure. Composition of the films was estimated by EDAX studies. XPSstudies indicated the binding energies corresponding to Zn(2p_3/2), Cd(3d_5/2 and 3d_3/2) and Se(3d_5/2 and 3d_3/2). Optical band gap of the films varied from 1.72 to 2.70 eV as the composition varied from CdSe to ZnSe side. Atomic forcestudies indicated grain size in the range of 20–150 nm. Photoelectrochemical cells were made with polysulphide as the redox electrolyte. The output was maximum for the photoelectrodes of composition Cd_0.9Zn_0.1Se.     

Physical and electrical properties of screen-printed Zn x Cd1−x thick films

Screen-printed thick films of Zn _x Cd_1–x S have been prepared in the entire composition range from pure CdS to pure ZnS and sintered at 800° C on alumina substrates. Their structural and electrical properties have been studied as a function ofx. X-ray diffraction analysis of Zn _x Cd_1–x S established the presence of wurtzite structure for the range 0 x 0.8, whereas forx = 1.0 the presence of the sphalerite structure of ZnS is observed. The lattice parametersa andc vary withx in accordance with Vegard's law. Scanning electron micrographs reveal an enhancement in porosity with increasingx. The dark electrical resistivity of the film increases withx in the range 0 x 0.6, but beyond this range it starts decreasing. Photoconductivity is studied as a function ofx. An effect of H₂ annealing on the dark resistivity and photo-sensitivity is established.     

Synthesis,Characterization and ESR Studies of Zn1−x Co x O Nanoparticles

Zn_1?x Co _x O polycrystalline nanoparticles with different (x=0.03, 0.05, 0.1, 0.15, 0.2, 0.25, and 0.3) compositions were synthesized using the sol-gel technique. The effects of doping ratio and annealing temperature on structure and magnetic properties were investigated systematically. The phase, crystal structure, and microstructure of the Zn_1?x Co _x O nanoparticles were characterized using X-Ray diffraction and scanning electron microscope. Electron spin resonance spectra of Zn_1?x Co _x O nanoparticles were collected at room temperature on a Bruker EMX model X-band spectrometer operating at a frequency of 9.50 GHz.     

Room temperature ferromagnetic behavior of Eu doped Cd1?x Zn x S nanoparticles

We report the structural and magnetic properties of the Eu doped Cd_1?x Zn _x S nanoparticles synthesized by wet chemical method. The idea is to exploit the room temperature magnetic behavior of nanoparticles. The particles size as observed by Transmission electron microscopy (TEM) and X-ray diffraction (XRD) is about 5 nm. The magnetic loop observed at room temperature using SQUID indicates the ferromagnetic behaviour of doped particles.     

Crystal Growth and Properties of Cd1 – x Zn x As2 Solid Solutions

Cd_{1 – x} Zn _x As₂ (x = 0.03, 0.05, 0.06) single crystals are grown by the Bridgman method, and their optical absorption spectra are measured. The introduction of Zn is shown to increase the band gap of CdAs₂, by up to 14 meV at x = 0.06. The highest content of ZnAs₂ incorporated into CdAs₂ is 6 mol %.     

Photoluminescence characteristics of synthesized copper doped Cd1−x Zn x S quantum dots

Free standing powders of copper-doped Cd_1?x Zn _x S (0 ≤ x ≤ 0.5) quantum dots (QDs) were synthesized using a simple chemical co-precipitation method. The copper concentration was varied from 0.01 to 10 at. wt% of Cd²⁺. X-ray diffraction and transmission electron microscope were used for crystallographic and morphological analyzes. Room temperature time resolved luminescence spectra were recorded using high peak power, pulsed N₂-laser excitation. Decay time values for bluish green and yellow emission have been calculated from recorded luminescence decay curves. Decay time dependence on Cu²⁺ and Zn²⁺ concentrations have been studied in detail. These QDs will have wide applications as nanophosphors, solar cells, photocatalysts and chemical sensors.     

Effects of Zn Doping on Superconductivity in Tl0.4K0.4Fe2−δ−x Zn x Se2

We have studied the transport and magnetic properties of the Tl_0.4K_0.4Fe_2?δ?x Zn _x Se₂ (nominal ratio 0.01≤x≤0.15) single crystal samples. It is found that although Zn doping leads to a decrease of charge carrier density, it does not affect the superconductivity significantly when x≤0.1. The doped superconductors exhibit properties similar to the parent compound (Tl_0.4K_0.4Fe_2?δ Se₂), e.g., the almost unchanged superconducting transition temperature (T _c) and the “hump”-like behavior in the resistivity curves, which denotes the transition from insulating phase to metallic phase. As the doping density rises, the hump obviously shifts to low temperature region, implying the quick enlargement of the ratio of insulating phase. The most plausible explanation for the above phenomena is that the Zn impurities prefer entering into the insulating phase only, therefore, merely hindering the formation of superconducting phase without directly changing its properties. The ESR measurement gives low signal-to-noise ratio and just weak paramagnetic signals, revealing strong itinerancy of the Zn doped superconductor.     

Atomic layer deposition of Zn1−x Mg x O:Al transparent conducting films

Aluminum-doped zinc magnesium oxide (Zn_1?x Mg _x O:Al) films with the Mg content from x = 0 to 0.48 were obtained using atomic layer deposition (ALD). Together with the thorough studies of the properties of the deposited films, the ALD growth parameters conditioning possible applications of Zn_1?x Mg _x O:Al films as transparent electrodes are investigated. Very low film resistivities (≤~10^?3 Ω cm) and the metallic-type conductivity behavior at room temperature for Zn_1?x Mg _x O:Al films are observed for Mg content x < 0.19. The Mg content of x = 0.19 results in the optical absorption edge of Zn_1?x Mg _x O:Al films at 3.81 eV (325 nm). Other film parameters like work function or sheet resistance can be easily modified by variation of growth parameters.     

Structural and optical properties of Cd x Zn(1 − x)Te thin films

Seven Cd _x Zn_{(1 ? x} Te solid solutions with x = 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 and 1.0 were synthesized by fusing stoichiometric amounts of CdTe and ZnTe constituents in silica tubes. Each composition was used in the preparation of a group of thin films of different thicknesses. Structural investigation of the obtained films indicates they have a polycrystalline structure with predominant diffraction lines corresponding to (111) (220) and (311) reflecting planes, which can be attributed to the characteristics of growth with the (111) plane. The optical constants (the refractive index n, the absorption index k, and the absorption coefficient α) of Cd _x Zn_{(1 \s -x)} Te thin films were determined in the spectral range 500–2000 nm. At certain wavelengths it was found that the refractive index, n, increases with increasing molar fraction, x. It was also found that plots of α² (hv) and α^1/2 (hv) yield straight lines, corresponding to direct and indirect allowed transitions respectively obeying the following two equations: $$\begin{gathered} E_g^d = 1.583 + 0.277x + 0.197x^2 \hfill \\ E_g^{ind} = 1.281 + 0.111x + 0.302x^2 \hfill \\ \end{gathered}$$      

Growth, characterization and transport properties of Pb x Zn1 − x S mixed crystals

The polycrystalline Pb _x Zn_1???x S semiconductor powder with (0 ≤ x ≤ 0·5) has been prepared by controlled co-precipitation method from an alkaline medium using thiourea as a sulphide ion source. Pellets are made with these powders applying 10 ton/sq cm pressure and sintered at 800 °C for 2 h in nitrogen atmosphere. X-ray studies of these samples have indicated that the compounds are polycrystalline in nature with mixed hexagonal and cubic structure of ZnS and cubic structure of PbS. Lattice parameters (a and c) of all the compounds are determined from the X-ray data and are found to decrease non-linearly with increase in Pb concentration (x). It is also observed that the grain size of the crystallites increases in samples with x = 0–0·5. Scanning electron micrographs have shown that both cubic and hexagonal crystallites are present in the mixed crystals. The electrical conductivity in Pb _x Zn_1???x S is found to decrease with increase in composition (x = 0–0·5), whereas it increases at all temperatures in all samples. Mobility of charge carrier concentration is found to increase with increasing temperature. The increase in carrier mobility in Pb _x Zn_1???x S samples may be due to reduced grain boundary potential. In Pb _x Zn_1???x S samples with x = 0–0·3, sum of the activation energy due to charge carriers and grain boundary potential is equal to the activation energy due to conductivity.     

Growth and characterization of Zn1 – x Mg x S thin films for electroluminescent applications

:Mn thin films (x=0–0.30) were prepared by thermal co-evaporation of ZnS, Mg and Mn. The structural investigation shows the solid solution is formed in the Mg composition range x=0–0.25 and phase segregation occurs at higher Mg composition (x > 0.25). The optical band gap shows an increase with increase of Mg composition. The electroluminescent emission corresponding to the transition ion shows a blue shift with increase of Mg composition in the film. :Mn films could be used as an active layer in a.c. thin film electroluminescent (ACTFEL) devices for obtaining green emission color.     

Growth and characteristics of ternary Zn1−x Mg x O films using magnetron co-sputtering

ZnMgO thin films with different Mg compositions were grown on Si (001) substrates by radio frequency magnetron co-sputtering, and their structural and optical properties have been investigated. As the Mg content was increased up to 10 at.%, the surface became smoother and the growth rate decreased. The strong peaks at 34.5–34.7^° corresponding to the (0002) diffraction peak of ZnMgO indicated the preferred growth along the c-axis. From the photoluminescence measurements, a shift of the emission peak and an increase of the activation energy were also observed with increasing Mg content.     

Electrical Properties of Cd x Zn1 – x As2 Solid Solutions at Pressures of up to 9 GPa

The electrical properties of n-type Cd_0.97Zn_0.03As₂ and Cd_0.95Zn_0.05As₂ single crystals are studied at hydrostatic pressures of up to 9 GPa. With increasing pressure, the carrier concentration in the solid solutions increases by more than three orders of magnitude, while their electrical resistivity drops by more than four orders of magnitude. In contrast to CdAs₂, the pressure dependences of resistivity for the solid solutions show no anomalies, which is interpreted as evidence that Zn consolidates the structure of CdAs₂, occupying vacant As sites.     

Study of Magnetic Properties in Spinels Co x Zn1?x Cr2O4 systems

The exchange interactions J _AA(x) and J _AB(x) are calculated by using a probability law for the Co _x Zn_1?x Cr₂O₄. The magnetic properties of a diluted ferromagnetic spinels Co _x Zn_1?x Cr₂O₄ system are investigated by using the high-temperature series expansions combined with the Padé approximants. The magnetic phase diagram, i.e., T _N versus?x, and the critical exponent associated with the magnetic susceptibility (??) are deduced.     

X-ray,electrical conductivity and infrared studies of the system Zn1−x CO x Mn1−x Fe x CrO4

The system Zn_1–x Co _x Mn_1–x Fe _x CrO₄ is tetragonal in the range 0.0x0.4 and cubic in the range 0.5x1. Electrical resistivity temperature behaviour obeys Wilson's law for all the compounds and thermoelectric coefficient values vary between 135 to 226V K^–1. All compounds exhibit P-type semiconductivity and possess low mobility values (10^–9 cm² V^–1 sec^–1). The infrared spectra show the presence of two strong absorption bands around 500 and 600 cm^–1. The probable ionic configuration for the system is suggested to be Zn _1–x ²⁺ Fe _x ^–y3+ -Co _x ²⁺ [Mn _1–x ³⁺ Fe _y ³⁺ CO _x ^–y2+ Cr³⁺]O₄.     

Transport anomalies in the Zn-substituted La2−x Sr x Cu1−y Zn y O4 with x ∼ 0.115; Possibility of the Pinning of CDW and SDW by Zn

Anomalies in the thermoelectric power and the Hall coefficient, which are analogous to those observed in La _2–x Ba _x CuO ₄ with x 1/8, have been observed in the Zn-substituted La _2–x Sr _x Cu _1–y Zn _y O ₄ with x = 0.115 and y = 0 – 0.025 and with x = 0.15 and y 0.02. Based on the so-called stripe model, these are explained as being due to the formation of the static order of the stripe-patterned CDW and SDW on account of the pinning by Zn. Accordingly, the long-standing problem on the conspicuous suppression of superconductivity in the Zn-substituted La _2–x Sr _x Cu _1–y Zn _y O ₄ with x 0.115 is likely to be attributed to this static order.     

Structural, optical, magnetic and electrical properties of Zn1−x Co x O thin films

Despite a considerable effort aiming at elucidating the nature of ferromagnetism in ZnO-based magnetic semiconductor, its origin still remains debatable. Although the observation of above room temperature ferromagnetism has been reported frequently in the literature by magnetometry measurement, so far there has been no report on correlated ferromagnetism in magnetic, optical and electrical measurements. In this paper, we investigate systematically the structural, optical, magnetic and electrical properties of Zn_1−x Co _x O:Al thin films prepared by sputtering with x ranging from 0 to 0.33. We show that correlated ferromagnetism is present only in samples with x > 0.25. In contrast, samples with x < 0.2 exhibit weak ferromagnetism only in magnetometry measurement which is absent in optical and electrical measurements. We demonstrate, by systematic electrical transport studies that carrier localization indeed occurs below 20–50 K for samples with x < 0.2; however, this does not lead to the formation of ferromagnetic phase in these samples with an electron concentration in the range of 6 × 10¹⁹ cm⁻³ ∼1 × 10²⁰ cm⁻³. Detailed structural and optical transmission spectroscopy analyses revealed that the anomalous Hall effect observed in samples with x > 0.25 is due to the formation of secondary phases and Co clusters.     

Optical, magnetic and structural characterization of Zn1 − x Co x O nanoparticles synthesized by solvothermal method

Nanoparticles of Co-doped ZnO with 3·8, 7·2 and 11·5 wt% were synthesized by solvothermal method through oxalate precursor route. X-ray diffraction studies showed the formation of hexagonal ZnO structure for x?= 0·038, however, secondary phase of Co₃O₄ arises on increasing the Co content up to 11·5%. Transmission electron microscopic studies showed that particles are in the nano-metric regime and the grain size decreases on increasing the Co concentration. Optical reflectance measurements showed an energy bandgap, which decreases on increasing Co concentration. Specific surface area of these nanoparticles was found to be very high and comes out to be 97·6, 112·1 and 603·8 m²g^???1, respectively. All the solid solutions showed paramagnetism with weak antiferromagnetic interactions. It is seen that the antiferromagnetic interaction increases on increasing Co concentration.     

Edge absorption and light propagation in single crystals of Zn1−x Cd x As2 solid solutions

The transmittance of Zn_1?x Cd _x As₂ anisotropic single crystals in their transparency region is found to depend on the incident light polarization, photon energy, and sample thickness. This effect is shown to be associated with light scattering in Zn_1?x Cd _x As₂, which can be understood in terms of the crystal structure of the monoclinic crystals. The fundamental absorption edge in Zn_1?x Cd _x As₂ is dominated by an indirect forbidden transition for the E ‖ c polarization and by a direct forbidden transition for E ⊥ c.