eV For Zn Research Articles

Zn1–xCdxO Microtubes: Synthesis and Optical Properties Using Direct Microwave Irradiation

AbstractHexagonal Zn1–xCdxO microtubes with CdO contents (x = 0, 1, 3 and 5 %) have been successfully synthesized via direct microwave irradiation. Field emission scanning electron microscopy (FE-SEM), UV–vis spectroscopy, photoluminescence (PL), and energy-dispersive spectrometer (EDS) were employed to characterize the Zn1–xCdxO microtubes. Zn1–xCdxO microtubes have an average diameter of 140 µm, wall thickness of 2~4 µm and length of about 250 µm. UV–vis studies showed that the optical band gap of ZnO microtube (3.27 eV) was reduced to 3.20 eV for Zn0.97Cd0.03O microtube. The PL spectra showed a strong emission peak in the visible region centered at 562.88 nm with a weak UV emission has been detected for Zn0.97Cd0.03O microtube. EDS confirms the presence of Zn and O in ZnO microtube and the absence of Cd as a doping material for CdO-doped ZnO microtubes due to the small amounts of CdO concentration.

Thin-film Cu(In,Ga)(Se,S)2 -based solar cell with (Cd,Zn)S buffer layer and Zn1−x Mg x O window layer

(Cd,Zn)S buffer layer and Zn1−xMgxO window layer were investigated to replace the traditional CdS buffer layer and ZnO window layer in Cu(In,Ga)(Se,S)2 (CIGSSe)-based solar cell. (Cd,Zn)S with band-gap energy (Eg) of approximately 2.6 eV was prepared by chemical bath deposition, and Zn1−xMgxO films with different [Mg]/([Mg] + [Zn]) ratios, x, were deposited by radio frequency magnetron co-sputtering of ZnO and MgO. The estimated optical Eg of Zn1−xMgxO films is linearly enhanced from 3.3 eV for pure ZnO (x = 0) to 4.1 eV for Zn0.6Mg0.4O (x = 0.4). The quality of the Zn1−xMgxO films, implied by Urbach energy, is severely deteriorated when x is above 0.211. Moreover, the temperature-dependent current density-voltage characteristics of the CIGSSe solar cells were conducted for the investigation of the heterointerface recombination mechanism. The external quantum efficiency of the CIGSSe solar cell with the (Cd,Zn)S buffer layer/Zn1−xMgxO window layer is improved in the wavelength range of 320–520 nm. Therefore, a gain in short-circuit current density up to about 5.7% was obtained, which is higher conversion efficiency of up to around 5.4% relative as compared with the solar cell with the traditional CdS buffer layer/ZnO window layer. The peak efficiency of 19.6% was demonstrated in CIGSSe solar cell with (Cd,Zn)S buffer layer and Zn1−xMgxO window layer, where x is optimized at 0.211. Copyright © 2017 John Wiley & Sons, Ltd.

Formation of TiO2 nanorods by Zn and Ti ion sequential implantation with enhanced visible optical absorption properties

TiO2 nanorods were fabricated by sequentially implanted with Zn and Ti ions into SiO2 substrate with post annealing in oxygen atmosphere at 1000°C. Comparing with single Ti ion implanted sample, the absorption edge of TiO2 nanorods showed a large red shift from 375nm to 450nm with its optical band gap reduced to about 2.5eV for Zn and Ti ions sequentially implanted samples. Microstructure analysis revealed that Zn was incorporated into TiO2 lattices which resulted in the band gap reduction. The results suggest that Zn and Ti ion sequential implantation is an effective way to synthesize TiO2 nanorods with enhanced visible light absorption.

Band alignment of atomic layer deposited MgO/Zn0.8Al0.2O heterointerface determined by charge corrected X-ray photoelectron spectroscopy

Pure magnesium (MgO) and zinc oxide doped with aluminum oxide (Zn0.8Al0.2O) were prepared via atomic layer deposition. We have studied the structure and band gap of bulk Zn0.8Al0.2O material by X-ray diffractometer (XRD) and Tauc method, and the band offsets and alignment of atomic layer deposited MgO/Zn0.8Al0.2O heterointerface were investigated systematically using X-ray photoelectron spectroscopy (XPS) in this study. Different methodologies, such as neutralizing electron gun, the use of C 1s peak recalibration and zero charging method, were applied to recover the actual position of the core levels in insulator materials which were easily influenced by differential charging phenomena. Schematic band alignment diagram, valence band offset (ΔEV) and conduction band offset (ΔEC) for the interface of the MgO/Zn0.8Al0.2O heterostructure have been constructed. An accurate value of ΔEV=0.72±0.11eV was obtained from various combinations of core levels of heterojunction with varied MgO thickness. Given the experimental band gaps of 7.83eV for MgO and 5.29eV for Zn0.8Al0.2O, a type-II heterojunction with a ΔEC of 3.26±0.11eV was found. Band offsets and alignment studies of these heterojunctions are important for gaining deep consideration to the design of various optoelectronic devices based on such heterointerface.

Key role of terminal hydroxyl groups and visible light in the reactive adsorption/catalytic conversion of mustard gas surrogate on zinc (hydr)oxides

Rhombic Zn(OH)2 and flower-like ZnO nano-particles were synthesized with a controlled precipitation rate. The materials were characterized by XRD, FTIR, potentiometric titration, nitrogen adsorption, TA-MS, MS-MS, SEM and UV–vis–NIR. A commercial ZnO was used as a reference material. Hydroxyl groups were formed on the surface when a slow addition of NaOH was used. The surface area of Zn(OH)2 was higher (350%) in comparison to that of ZnO. The presence of hydroxyl groups increased the band gap from 3.05eV for ZnO to 3.22eV for Zn(OH)2. The materials were used as reactive adsorbents of mustard gas surrogate, 2-Chloroethyl ethyl sulfide (CEES). On the surface of Zn(OH)2, more CEES was absorbed than of that of ZnO. Moreover, the capacity on Zn(OH)2 significantly increased under a visible light exposure. The results indicated the paramount role of terminal OH groups in the reactive adsorption process. The porosity was also found important since it affects the distribution of these OH active centers. Ethyl vinyl sulfide (EVS) was detected on the surfaces of both samples. At light, hydroxyethyl ethyl sulfide (HEES) was detected only on Zn(OH)2. Thus the absorption of photons led to the formation of the ethyl ethyl sulfide (EES) cations, which were transformed to less toxic EVS by dehydrohalogenation. With water and hydroxyl groups on the surface, the light irradiation promoted the formation of hydroxyl radicals. They reacted with the EES radicals and formed HEES via a hydrolysis pathway. No conversion of CEES was found in the dark.

Band alignment of Zn0.778Cd0.222O/MgO(0 0 1) heterointerface determined by X-ray photoelectron spectroscopy

Ternary Zn0.778Cd0.222O thin film oriented along c-axis has been successfully deposited on cubic MgO(001) substrate by pulsed laser deposition and no detectable phase separation at this concentration. The band offset properties at the interface of the Zn0.778Cd0.222O/MgO(001) heterojunction has also been experimentally studied by X-ray photoelectron spectroscopy. The valence-band offset is determined to be 4.67±0.30eV. The heterojunction shows type-I band configuration with a conduction-band offset of 0.25±0.35eV by using the experimental bandgaps of 2.91±0.05eV for Zn0.778Cd0.222O and 7.83eV for MgO. The value for conduction-band offset (0.25eV) is lower than that of valence-band offset (4.67eV), suggesting that transport is mainly dominated by electrons. The accurate determination of the band alignment of Zn0.778Cd0.222O/MgO heterojunction facilitates the design of optical and electronic devices based on Zn0.778Cd0.222O/MgO structure.

Experimental determination of band offsets of NiO-based thin film heterojunctions

The energy band diagrams of NiO-based solar cell structures that use various n-type oxide semiconductors such as ZnO, Mg0.3Zn0.7O, Zn0.5Sn0.5O, In2O3:Sn (ITO), SnO2, and TiO2 were evaluated by photoelectron yield spectroscopy. The valence band discontinuities were estimated to be 1.6 eV for ZnO/NiO and Mg0.3Zn0.7O/NiO, 1.7 eV for Zn0.5Sn0.5O/NiO and ITO/NiO, and 1.8 eV for SnO2/NiO and TiO2/NiO heterojunctions. By using the valence band discontinuity values and corresponding energy bandgaps of the layers, energy band diagrams were developed. Judging from the band diagram, an appropriate solar cell consisting of p-type NiO and n-type ZnO layers was deposited on ITO, and a slight but noticeable photovoltaic effect was obtained with an open circuit voltage (Voc) of 0.96 V, short circuit current density (Jsc) of 2.2 μA/cm2, and fill factor of 0.44.

Band alignments of different buffer layers (CdS, Zn(O,S), and In2S3) on Cu2ZnSnS4

The heterojunctions of different n-type buffers, i.e., CdS, Zn(O,S), and In2S3 on p-type Cu2ZnSnS4 (CZTS) were investigated using X-ray Photoelectron Spectroscopy (XPS) and Near Edge X-ray Absorption Fine Structure (NEXAFS) Measurements. The band alignment of the heterojunctions formed between CZTS and the buffer materials was carefully measured. The XPS data were used to determine the Valence Band Offsets (VBO) of different buffer/CZTS heterojunctions. The Conduction Band Offset (CBO) was calculated indirectly by XPS data and directly measured by NEXAFS characterization. The CBO of the CdS/CZTS heterojunction was found to be cliff-like with CBOXPS = −0.24 ± 0.10 eV and CBONEXAFS = −0.18 ± 0.10 eV, whereas those of Zn(O,S) and In2S3 were found to be spike-like with CBOXPS = 0.92 ± 0.10 eV and CBONEXAFS = 0.87 ± 0.10 eV for Zn(O,S)/CZTS and CBOXPS = 0.41 ± 0.10 eV for In2S3/CZTS, respectively. The CZTS photovoltaic device using the spike-like In2S3 buffer was found to yield a higher open circuit voltage (Voc) than that using the cliff-like CdS buffer. However, the CBO of In2S3/CZTS is slightly higher than the optimum level and thus acts to block the flow of light-generated electrons, significantly reducing the short circuit current (Jsc) and Fill Factor (FF) and thereby limiting the efficiency. Instead, the use of a hybrid buffer for optimization of band alignment is proposed.

Essential role of catalysts (Mn, Au, and Sn) in the vapor liquid solid growth kinematics of ZnS nanowires

In this paper, we demonstrate that surface energy of the catalyst is a vital parameter for the growth rate, self doping of the self assembled nanowires synthesized by employing vapor liquid solid growth technique. The synthesis of ZnS nanowires was done by selectively using three different catalysts (Mn, Au, and Sn), where Au, is the most common catalyst, was used as a reference. The distinctive difference in the growth rate was due to the surface energy of the metal alloy droplet and the interface energies, as explained theoretically using thermodynamic approach. We have found that the activation energy of diffusion of (Zn, S) species in the catalyst droplet was low in Sn (0.41 eV for Zn and 0.13 eV for S) and high in Mn (1.79 eV for Zn and 0.61 eV for S) compared to Au (0.62 eV for Zn and 0.21 eV for S) catalyzed ZnS nanostructures. The thermodynamic calculations predicted the growth rates of Sn (7.5 nm/s) catalyzed nanowires was faster than Au (5.1 nm/s) and Mn (4.6 nm/s) catalyzed ZnS nanostructures, which were in agreement with the experimental results. Finally, the location of the catalyst as dopant in the grown nanostructure was predicted and compared with experimental observations.

Chalcopyrite semimagnetic semiconductors: From nanocomposite to homogeneous material

Currently, complex ferromagnetic semiconductor systems are of significant interest due to their potential applicability in spintronics. A key feature in order to use semiconductor materials in spintronics is the presence of room temperature ferromagnetism. This feature was recently observed and is intensively studied in several Mn-alloyed II-IV-V2 group diluted magnetic semiconductor systems. The paper reviews the origin of room temperature ferromagnetism in II-IV-V2 compounds. In view of our recent reports the room temperature ferromagnetism in Mn-alloyed chalcopyrite semiconductors with more than 5 molar % of Mn is due to the presence of MnAs clusters. The solubility of magnetic impurities in bulk II-IV-V2 materials is of the order of a few percent, depending on the alloy composition. High values of the conducting hole - Mn ion exchange constant Jpd have significant value equal to 0.75 eV for Zn0.997Mn0.003GeAs2. The sample quality has significant effect on the magnetotransport of the alloy. The magnetoresistance of the alloy change main physical mechanism from spin-disorder scattering and weak localization for homogeneous samples to cluster-related geometrical effect observed for nanocomposite samples. The magnetoresistance of the II-IV-V2 alloys can be then tuned up to a few hundreds of percent via changes of the chemical composition of the alloy as well as a degree of disorder present in a material.

Green route fast synthesis and characterization of chemical bath deposited nanocrystalline ZnS buffer layers

Zinc sulphide (ZnS) thin films are deposited using chemical bath deposition method on the glass substrates in an aqueous alkaline reaction bath of zinc acetate and thiourea along with non-toxic complexing agent tri-sodium citrate at 95 °C. The results show noteworthy improvement in the growth rate of the deposited ZnS thin films and thickness of the film increases with the deposition time. From X-ray diffraction patterns, it is found that the ZnS thin films exhibit hexagonal polycrystalline phase reflecting from (101) and (0016) planes. The high resolution transmission electron microscopy studies confirmed the formation of hexagonal phase from the d-value calculation which was 0.3108 nm. X-ray photoelectron spectroscopy reveals that the Zn–S bonding energy is at 1022.5 and 162.1 eV for Zn 2p3/2 and S 2p1/2 states, respectively. Field emission scanning electron microscopy study shows that deposited thin films are highly uniform, with thin thickness and completely free from large ZnS clusters which usually form in aqueous solutions. Atomic force microscopy investigates that root mean square values of the ZnS thin films are from 3 to 4.5 nm and all the films are morphologically smooth. Energy dispersive spectroscopy shows that the ZnS thin films are relatively stoichiometric having Zn:S atomic ratio of 55:45. It is shown by ultraviolet–visible spectroscopy that ∼90% transmittance and ∼10% absorbance for the ZnS films in the visible region, which is significantly higher than that reported elsewhere and the band gap energy of the ZnS films is found to be 3.76, 3.74, and 3.71 eV, respectively.

High‐Performance Red, Green, and Blue Electroluminescent Devices Based on Blue Emitters with Small Singlet–Triplet Splitting and Ambipolar Transport Property

AbstractTwo coordination complex emitters as well as host materials Be(PPI)2 and Zn(PPI)2 (PPI = 2‐(1‐phenyl‐1H‐phenanthro[9,10‐d]imidazol‐2‐yl)phenol) are designed, synthesized, and characterized. The incorporation of the metal atom leads to a twisted conformation and rigid molecular structure, which improve the thermal stability of Be(PPI)2 and Zn(PPI)2 with high Td and Tg at around 475 and 217 °C, respectively. The introduction of the electron‐donating phenol group results in the emission color shifting to the deep‐blue region and the emission maximum appears at around 429 nm. This molecular design strategy ensures that the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) HOMO and LUMO of Be(PPI)2 and Zn(PPI)2 localize on the different moieties of the molecules. Therefore, the two complexes have an ambipolar transport property and a small singlet–triplet splitting of 0.35 eV for Be(PPI)2 and 0.21 eV for Zn(PPI)2. An undoped deep‐blue fluorescent organic light‐emitting device (OLED) that uses Be(PPI)2 as emitter exhibits a maximum power efficiency of 2.5 lm W−1 with the CIE coordinates of (0.15, 0.09), which are very close to the National Television Standards Committee (NTSC) blue standard (CIE: 0.14, 0.08). Green and red phosphorescent OLEDs (PhOLEDs) that use Be(PPI)2 and Zn(PPI)2 as host materials show high performance. Highest power efficiencies of 67.5 lm W−1 for green PhOLEDs and 21.7 lm W−1 for red PhOLEDs are achieved. In addition, the Be(PPI)2‐based devices show low‐efficiency roll‐off behavior, which is attributed to the more balanced carrier‐transport property of Be(PPI)2.

First principle study on the electronic and magnetic properties in Zn0.75Cr0.25M (M = S, Se, Te) semiconductors

Using the first-principle method, the structural, electronic and magnetic properties of Zn0.75Cr0.25M (M=S, Se, Te) have been investigated. The calculated formation energy and cohesive energy of Zn0.75Cr0.25M are negative and the absolute values of them decrease with the increase of atomic radius as well as the electronegativity of the anions. Zn0.75Cr0.25M display half-metallic characteristics with energy band gaps of 1.06, 0.65 and 0.83eV, respectively. The conventional gaps for minority spin are 2.91, 2.16 and 1.75eV for Zn0.75Cr0.25S, Zn0.75Cr0.25Se and Zn0.75Cr0.25Te respectively, which decrease with the increase of anion radius successively, similar to that observed in the binary compounds of ZnM. For all the three materials, exchange splitting energies Δx(pd) due to the effect of Cr 3d state are negative, implying that the effective potential is more attractive for minority spin than that for majority spin, and the absolute value of Δx(pd) decreases with the increase of atomic radius of anions. The calculated positive values of N0α suggest interactions between Zn-s and Cr-3d states are repulsive, while the negative values of N0β show that p–d interactions at the valence band are more attractive. All these conclusions demonstrate that Zn0.75Cr0.25M are promising candidates for practical applications in spintronics.

Comparative Study of Temperature Dependent Barrier Heights of Pd/ZnO Schottky Diodes Grown along Zn- and O-Faces

In this study, the effect of polar face on Schottky barrier diodes has been investigated. Two samples of ZnO were grown hydrothermally under similar growth conditions. The Palladium (Pd) metal contacts of area 0.78 mm2 were fabricated on both faces and were studied comprehensively using DLS-83 Deep Level Spectrometer over temperature range of 160K330K. The current-voltage (IV) measurements revealed that the ideality factor n and barrier height ϕB were strongly temperature dependent for both faces (Zn and O-face) of ZnO, indicating that the thermionic emission is not the dominant process, which showed the inhomogenity in the barrier heights of grown samples. This barrier height inhomogenity was explained by applying Gaussian distribution model. The extrapolation of the linear ϕap verses n plot to n = 1 has given a homogeneous barrier height of approximately 0.88±0.01 eV and 0.76±0.01 eV for Zn and O-faces respectively. ϕap versus 1/T plot was drawn to obtain the values of mean barrier height for Zn and O-face (0.88±0.01 eV, 0.76±0.01 eV) and standard deviation (δs) (0.015±0.001 V, 0.014±0.001 V) at zero bais respectively. The value of δs for the Zn-face is larger than O-face, showing that inhomogenity in the barrier heights is more in the sample grown along Zn-face as compared to the sample grown along O-face.

First-principles calculations of Cd-doped ZnO thin films deposited by pulse laser deposition

Zn1−xCdxO thin films are deposited on quartz substrate by pulse laser deposition. Their band structure and optical properties are experimentally and theoretically investigated. By varying Cd concentration, the band gap of Zn1−xCdxO films can be adjusted in a wide range from 3.219 eV for ZnO to 2.197 eV for Zn0.5Cd0.5O, which produces different emissions from ultraviolet to Kelly light in their photoluminescence spectra. Simultaneity, the electronic structure and band gap of Zn1−xCdxO are investigated by the density functional theory (DFT) with a combined generalized gradient approximation (GGA) plus Hubbard U approach, which precisely predicts the band-gaps of ZnO and Zn1−xCdxO alloys. Both the experimental results and theoretical simulation reveal that with increasing Cd concentration in Zn1−xCdxO alloys, their absorption coefficients in visible light range are evidently enhanced. The adjustable photoluminescence emission and enhanced visible light absorption endow Zn1−xCdxO alloys potential applications in optoelectronic and photocatalytic fields.

Structural and optical analysis of ZnBeMgO powder and thin films

We here report the structural and optical studies of Zn 1− x− y Be x Mg y O (0 ≤ x ≤ 0.15; 0 ≤ y ≤ 0.20) powders and thin films. From the Rietveld refinement of the powder X-ray diffraction (XRD) patterns it was revealed that the value of ‘ a’ lattice parameter remains almost unchanged whereas ‘ c’ parameter reduces with Be and Mg co-doping in ZnO. The Zn-O bond length also decreases in co-doped samples. Raman studies of the pure ZnO powder showed all the characteristic peaks of the wurtzite hexagonal structure and with (Be, Mg) co-doping new modes appeared which can be attributed to arise as a result of substitution. The XRD of the films prepared from the powders using pulsed laser deposition (PLD) technique exhibited the preferential orientation and with increase in co-doping the (0 0 0 2) peak also shifts to higher 2 θ values suggesting the incorporation of Be/Mg at the Zn-site. From the UV–visible optical transmittance measurement it was noticed that the band gap of the pristine ZnO film is 3.3 eV which enhanced up to 4.51 eV for Zn 0.7Be 0.1Mg 0.2O film which lies in the solar blind region and is very useful in the realization of deep UV detectors.

Structural and optical studies on antimony and zinc doped CuInS2 thin films

The influence of Zn and Sb impurities on the structural, optical and electrical properties of CuInS2 thin films on corning 7059 glass substrates was studied. Undoped and Zn or Sb doped CuInS2 thin films were deposited by thermal evaporation method and annealed in vacuum at temperature of 450 ∘C Undoped thin films were grown from CuInS2 powder using resistively heated tungsten boats. Zn species was evaporated from a thermal evaporator all together to the CuInS2 powder and Sb species was mixed in the starting powders. The amount of the Zn or Sb source was determined to be in the range 0–4 wt% molecular weight compared with the CuInS2 alloy source. The films were studied by means of X-ray diffraction (XRD), Optical reflection and transmission and resistance measurements. The films thicknesses were in the range 450–750 nm. All the Zn: CuInS2 and Sb: CuInS2 thin films have relatively high absorption coefficient between 104 cm−1 and 105 cm−1 in the visible and the near-IR spectral range. The bandgap energies are in the range of 1.472–1.589 eV for Zn: CuInS2 samples and 1.396–1.510 eV for the Sb: CuInS2 ones. The type of conductivity of these films was determined by the hot probe method. Furthermore, we found that Zn and Sb-doped CuInS2 thin films exhibit P type conductivity and we predict these species can be considered as suitable candidates for use as acceptor dopants to fabricate CuInS2-based solar cells.

A spectroscopic ellipsometric investigation of new critical points of Zn 1− xMn xS epilayers

Zn 1− x Mn x S epilayers were grown on GaAs (1 0 0) substrates by hot-wall epitaxy. X-ray diffraction (XRD) patterns revealed that all the epilayers have a zincblende structure. The optical properties were investigated using spectroscopic ellipsometry at 300 K from 3.0 to 8.5 eV. The obtained data were analyzed for determining the critical points of pseudodielectric function spectra, 〈 ɛ( E)〉 = 〈 ɛ 1( E)〉 + i〈 ɛ 2( E)〉, such as E 0, E 0 + Δ 0, and E 1, and three E 2 (Σ, Δ, Γ) structures at a lower Mn composition range. These critical points were determined by analytical line-shapes fitted to numerically calculated derivatives of their pseudodielectric functions. The observation of new peaks, as well as the shifting and broadening of the critical points of Zn 1− x Mn x S epilayers, were investigated as a function of Mn composition by ellipsometric measurements for the first time. The characteristics of the peaks changed with increasing Mn composition. In particular, four new peaks were observed between 4.0 and 8.0 eV for Zn 1− x Mn x S epilayers, and their characteristics were investigated in this study.

Zno-based thin films synthesized by atmospheric pressure mist chemical vapor deposition

An atmospheric pressure mist chemical vapor deposition (mist-CVD) system has been developed to prepare zinc oxide (ZnO)-based thin films. This is a promising method for large-area deposition at low temperatures taking into account of its simplicity, inexpensiveness, and safety. Nominally pure ZnO, Al-doped n-type ZnO (ZnO:Al), and N-doped p-type ZnO (ZnO:N) thin films, as well as Zn 1− x Cd x O and Zn 1− y Mg y O alloy films, have been deposited by this mist-CVD system. The films deposited at the temperatures ranging from 400 to 500 °C were of an acceptable crystallinity with (0 0 2) preferential orientation and homogeneous surface. All the films exhibited high transmittance of about 90% in visible regions and dominant UV emission in the photoluminescence spectra. The n-type ZnO:Al films had a low resistivity of 1.08×10 –3 Ω cm at an optimal Al content of 4 at%. The p-type conductivity was obtained in ZnO:N films annealed at higher temperatures with a resistivity of 72.8 Ω cm, Hall mobility of 2.28 cm 2 V −1 s −1, and hole concentration of 3.76×10 16 cm −3, as confirmed by Hall-effect measurements. A hydrogen-assisted nitrogen-doping mechanism was proposed to answer for the realization of p-type conductivity in ZnO. The films of Zn 1− x Cd x O and Zn 1− y Mg y O ternary alloys were also deposited by this technique. The band gap energies, for instance, were 3.05 eV for Zn 1− x Cd x O ( x=0.06), 3.28 eV for ZnO, and 3.56 eV for Zn 1− y Mg y O ( y=0.11), as confirmed by the optical absorption spectra. The band gap engineering could be readily realized in the ZnO system using mist-CVD.

Ionization potentials of Zn, Cd, Hg and dipole polarizabilities of Zn+, Cd+, Hg+: correlation and relativistic effects

Abstract The ionization potentials (IPs) of the group IIB metals and the electric dipole polarizabilities of their positively charged ions were calculated using the relativistic one-component spin averaged Douglas–Kroll (DK) no pair approximation combined with the CCSD(T) treatment of the electron correlation. Ionization potentials 9.393 (9.394) eV for Zn and 8.941 (8.993) eV for Cd agree with experimental values (in parentheses) excellently and the IP for Hg, 10.362 (10.437) eV agrees with experiment reasonably well. The three factors that can affect the accuracy, i.e. basis set effects, electron correlation and relativistic effects, were carefully examined.