Cd Composition Research Articles

Low excess noise HgCdTe e-SWIR avalanche photodiode operating at high gain and temperature

The Hg1−xCdxTe material can exhibit a pure electron avalanche when the composition of the Cd is below 0.6. This hole-to-electron impact ionization ratio close to zero results in noiseless gain. In this paper, we present the results on the gain and noise characteristics of the extended short wavelength infrared (e-SWIR) HgCdTe electron-initialed avalanche photodiodes (e-APDs). The e-APD has a Cd composition of 0.4 and a cutoff wavelength of 3.1μm. At 80 K with a bias voltage of −18.5 V, the device achieves a remarkable gain of 1080, with an excess noise factor below 1.6. Furthermore, the device maintains a gain of 550 and an excess noise below 1.6 at 220 K. Notably, this work reports for the first time the low noise performance of the device at high temperatures and high gain. Moreover, we investigate the responsivity and detectivity of the device when operating at the unit gain point.

Mid-infrared modulated photoluminescence mapping to investigate in-plane distributions of bandedge transitions in As-doped HgCdTe

In-plane distribution of band edge electronic structure of the narrow-gap arsenic (As)-doped HgCdTe is a crucial topic fundamentally and technically for mid-infrared detector array but hard to be investigated for long experimentally. This work reports a demonstration of the modulated photoluminescence (PL) mapping carried on As-doped HgCdTe, with the spatial resolution of a typical array pixel scale and with the elaborate band edge transitions being distinguished. Curve fittings related to the bandgap and to the impurities of Hg vacancy (VHg), As donor (AsHg), and AsHg–VHg pair are confirmed for PL mapping assisted by a temperature-dependent PL analysis. The spatial non-uniformity of Cd composition and the distributions of impurity relative concentrations are derived. Correlation analysis suggests that the As atom directly replacing the Hg atom in the complete lattice and the As atom occupying the already-existing VHg are the two approaches for the AsHg formation during As doping. The non-uniform band edge properties may lead to the in-plane conductivity fluctuation detrimental to the array performance. The results indicate the significance of probing the band edge impurity uniformity of As-doped HgCdTe for arrays fabrication, and the modulated PL mapping serving as a desirable and effective tool.

Structural properties and defect formation mechanisms in MBE-grown HgCdTe on InSb (211)B substrates

This work investigates the structural properties of HgCdTe thin films grown on InSb (211)B substrates using molecular beam epitaxy (MBE). The Cd composition of thin films is accurately determined using non-destructive approaches based on x-ray diffraction (XRD) and reflectance infrared spectroscopy. The as-grown HgCdTe thin films exhibit characteristic surface defects with a size of 7–10 μm and density of ∼105 cm−2, resulting in an additional spread in XRD full width at half maximum. Cross-sectional transmission electron microscopy results indicate that these defects are caused by surface In droplet formation during the oxide removal process of InSb substrate, which subsequently results in the formation of In4Te3 inclusions and extended defects in MBE-grown HgCdTe. Our findings provide additional confirmation that suppressing thermally induced damage of the InSb substrate is necessary for fabricating high-performance infrared detectors using HgCdTe grown on InSb substrates.

Tracing acid mine drainage and estuarine Zn attenuation using Cd and Zn isotopes

It has been estimated that the acid mine drainage (AMD) impacted Odiel river basin in southern Spain supplies 0.37% and 15% of the global riverine fluxes of Cd and Zn to the oceans, respectively (Sarmiento et al., 2009). However, the behaviour of Cd and Zn in the Ria of Huelva estuary, which connects the Odiel and Tinto watersheds with the Gulf of Cadiz, has yet to be fully investigated. Furthermore, very few studies have investigated Cd and Zn isotope behaviour in estuaries worldwide. This study presents Cd and Zn concentrations and isotopic compositions for the Ria of Huelva estuary and surrounding watersheds, sampled in 2017 and 2019. Sulfide-rich rock samples extracted from three mines yield Cd and Zn isotope compositions that range from –0.14‰ to +0.07‰ (n = 4) for δ114Cd and –0.01‰ to +0.29‰ (n = 4) for δ66Zn. However, a uniform riverine signal of about +0.02‰ for Cd and +0.17‰ for Zn indicates that tracing of individual mining regions using Cd and Zn isotopes is challenging. Limited variability was observed in dissolved δ114Cd values throughout the watershed, including AMD, the estuary, and the Gulf of Cadiz, with a mean value of ±0.00 ± 0.13‰ (n = 25, 2 SD; excludes one AMD outlier, at +0.48‰), including both 2017 and 2019 data. By contrast, δ66Zn values ranged from –0.12‰ to +0.35‰ (n = 28) for the same geographical and temporal scope. In May 2017, a large spill from an abandoned mine, La Zarza, resulted in a drastic increase in the concentrations of trace metals reaching the estuary compared to 2019, but no impact of this mine spill on Cd or Zn isotope compositions is observed. In 2019, an increase in δ66Zn values in the estuary coincided with high pH values (up to pH = 8.8) and chloride concentrations (2.73%), which may reflect an alkaline anthropogenic input from the active neighbouring industrial complex. Overall, Cd concentrations and isotope compositions in the estuary are largely consistent with conservative mixing behaviour. By contrast, Zn behaviour is non-conservative, with removal of 49–97% of dissolved riverine Zn in the estuary during the period 2017–2019, associated with a relatively small isotopic shift to lighter Zn isotope compositions. Removal of Zn to the particulate phase in the Ria of Huelva estuary therefore largely attenuates high riverine Zn fluxes from AMD, indicating that previously estimated Odiel river basin Zn fluxes were overestimated. Nevertheless, the variable but generally light AMD Cd and Zn isotope compositions, coupled with high dissolved metal concentrations, suggest that Cd and Zn isotopes may be useful tracers of regionally averaged AMD inputs to the Gulf of Cadiz and beyond.

Improved responsivity and detectivity of LPE HgCdTe short-wavelength infrared photodetector by tuning the composition gradient

This work introduces an effective way to improve the responsivity and detectivity of liquid phase epitaxy (LPE) HgCdTe avalanche focal plane array (FPA) for short-wavelength infrared (SWIR) signal detection by tuning the composition gradient. It is contributed to the Hg-Cd interdiffusion at the HgCdTe/CdZnTe interface during the heat treatment. The Cd composition can be redistributed, which gives different composition (band gap) in the absorption and multiplication regions. The newly designed FPA achieves a 50% improvement in responsivity (gain) and a 30% increase in detectivity over the conventional SWIR FPA (−3 V, 80 K). The newly designed FPA also exhibits a superior performance at 130 K than the conventional FPA at 80 K.

Zinc Supply Affects Cadmium Uptake and Translocation in the Hyperaccumulator Sedum Plumbizincicola as Evidenced by Isotope Fractionation.

This study employs stable isotope analysis to investigate the mechanisms of cadmium (Cd) and zinc (Zn) interaction in the metal hyperaccumulating plant species Sedum plumbizincicola. To this end, the Cd and Zn isotope compositions of root, stem, leaf, and xylem sap samples were determined during metal uptake and translocation at different Cd and Zn concentrations. The enrichment of light isotopes of both elements in plants during uptake was less pronounced at low metal supply levels, likely reflecting the switch from a low-affinity to a high-affinity transport system at lower levels of external metal supply. The lower δ114/110Cd values of xylem sap when treated with a metabolic inhibitor decreasing the active Cd uptake further supports the preference of heavier Cd isotopes during high-affinity transport. The Δ66Znplant-initialsolution or Δ66Znplant-finalsolution values were similar at different Cd concentrations, indicating negligible interaction of Cd in the Zn uptake process. However, decreasing Zn supply levels significantly increased the enrichment of light Cd isotopes in plants (Δ114/110Cd = -0.08‰) in low-Cd treatments but reduced the enrichment of light Cd isotopes in plants (Δ114/110Cd = 0.08‰) under high Cd conditions. A systematic enrichment of heavy Cd and light Zn isotopes was found in root-to-shoot translocation of the metals. The Cd concentrations of the growth solutions thereby had no significant impact on Zn isotope fractionation during root-to-shoot translocation. However, the Δ114/110Cdtranslocation values hint at possible competition between Cd and Zn for transporters during root-to-shoot transfer and this may impact the transport pathway of Cd. The stable isotope data demonstrate that the interactions between the two metals influenced the uptake and transport mechanisms of Cd in S. plumbizincicola but had little effect on those of Zn.

Correlating fractography with mechanical properties of microalloyed 2219Al alloys under different thermo-mechanical conditions

ABSTRACT 2219Al alloys microalloyed with varying trace contents (0–0.1 wt.%) of Cd were cast, and subjected to standard sequential thermo-mechanical processes of rolling and age-hardening treatments. Uniaxial tensile and Charpy impact tests were performed, and fractured surfaces were studied under scanning electron microscope (SEM). Variations in tensile ductility and toughness with trace additions of Cd were reported under given processing conditions. Independent influences of Cd compositions, peak-ageing treatment and rolling were investigated to identify predominant fracture modes (ductile/fibrous, brittle/cleavage or mixed) of 2219Al alloys for the first time. Salient features and fracture mechanisms as exhibited from the fractographs were further correlated with microstructural evolution, mechanical ductility and toughness. Cast 2219Al alloy exhibited typically ductile fractographs, compared to moderate level of ductility after microalloying. Lower fracture strain and toughness of peak-aged alloys were accompanied with mixed mode of fracture surfaces. Rolling resulted in fractographs of mixed mode, however with higher ductility compared to peak-aged alloys. Impact testing resulted in failure at higher strain rate, exhibiting typically brittle fractographs, correlated with the impact toughness values. Present fractographic analysis provided a structure-property correlation, to validate the susceptibility of these alloys, to different modes of failure, subjected under various loading and thermo-mechanical treatments.

Environmental Risk from Organic Residues

Soil nutrient imbalance is a global threat to food security and ecosystem sustainability but adding organic residues or constructing anthropogenic soils and technosols can optimize it. However, FAO considers organic residues not “risk-free”, mainly due to their heavy metal content. Despite the fact that applying pruning residues to soil is a worldwide fertilization practice, its potential heavy metal risk has been poorly studied. This work characterizes Cu, Zn, Cd, Cr, Ni and Pb elemental composition concentration and their solubility content in almond tree pruning, commercial peat substrate, hay straw, olive tree pruning, pomegranate peel, pine needle, date palm leaf pruning, sewage sludge compost and vine pruning. Furthermore, we compare the legal frameworks governing heavy metal content in agricultural substrates to heavy metal concentration in each residue. Results show that commercial peat substrate is the only one among those studied that surpasses the threshold value for Cr in agricultural substrates. All pruning residues met the heavy metal threshold value; hence, their application to soil involves minimal soil toxicity. Moreover, the solubility index of heavy metals and the maximum quantity of each residue are crucial to discerning a heavy metal-free organic fertilization plan.

Disorder-induced topological phase transition in HgCdTe crystals

Using the self-consistent Born approximation, we study a topological phase transition appearing in bulk HgCdTe crystals induced \emph{uncorrelated} disorder due to both randomly distributed impurities and fluctuations in Cd composition. By following the density-of-states evolution, we clearly demonstrate the topological phase transition, which can be understood in terms of the disorder-renormalized mass of Kane fermions. We find that the presence of heavy-hole band in HgCdTe crystals leads to the topological phase transition at much lower disorder strength than it is expected for conventional 3D topological insulators. Our theoretical results can be also applied to other narrow-gap zinc-blende semiconductors such as InAs, InSb and their ternary alloys InAsSb.

Controlling electrical and optical properties of wurtzite CdxZn1−xO with high Cd contents via native defects manipulation by low-temperature annealing

Bandgap energies in wurtzite (WZ) structured CdxZn1−xO alloys are known to decrease with increasing Cd content (x). Our previous work demonstrated that WZ-CdxZn1−xO alloys with a high Cd content of x ∼ 0.6 and a low gap of 2 eV can be stabilized by oxygen interstitials when grown in an O-rich environment. However, such O-rich WZ-CdxZn1−xO alloys have poor electrical properties due to compensating native defects. In this work, we synthesized pure WZ phase CdxZn1−xO thin films with different Cd contents by magnetron sputtering in an oxygen-rich environment. Changes in structural, electrical, and optical properties of these O-rich wurtzite CdxZn1−xO after rapid thermal annealing were investigated. While alloys with a low Cd composition of 0.2 can maintain a pure wurtzite structure up to 500 °C, phase separation occurs at a lower annealing temperature of ∼400 °C for Cd-rich (x = 0.6) films. Isochronal and isothermal annealing studies reveal the kinetics of native defects in these alloys. Highly mobile hydrogen interstitial donor defects, oxygen interstitials, and more stable cation vacancies outdiffuse sequentially as the annealing temperature increases from <300 to >400 °C. By exploiting the difference in the energy barrier between acceptor defects removal and phase separation, a pure wurtzite phase alloy with a low bandgap of 2 eV and decent electrical properties was realized by annealing O-rich WZ-Cd0.6Zn0.4O at 300 °C with an extended annealing duration of >100 s. These results demonstrate a practical way to obtain low-gap oxide semiconductors with strong optical absorption and controllable electrical conductivities.

SRH suppressed P-G-I design for very long-wavelength infrared HgCdTe photodiodes.

The very long wavelength infrared (VLWIR, >14 µm) spectral band is an indispensable part of new-generation infrared remote sensing. Mercury cadmium telluride (HgCdTe or MCT) has shown excellent potential across the entire infrared band. However, the dark current, which is extremely sensitive to the technological level and small Cd composition, severely limits the performance of VLWIR HgCdTe photodiodes. In this study, cut-off wavelengths of up to 15 µm for HgCdTe devices with novel P-G-I (including wide bandgap p-type cap layer, grading layer and intrinsic absorption layer) designs have been reported. Compared with a device with a double-layer heterojunction (DLHJ) structure, the designed P-G-I structure successfully reduced dark current by suppressing the Shockley-Read-Hall process. Considering the balance of quantum efficiency and dark current, with the introduction of an approximately 0.8 µm thickness Cd composition grading layer, the device can achieve a high detectivity of up to 2.5×1011 cm Hz1/2 W-1. Experiments show that the P-G-I-T device has a lower dark current and a better SRH process suppressing ability than DLHJ devices, the measured detectivity achieved 8.7×1010 cm Hz1/2 W-1. According to additional research, the trap-assisted tunneling current is the primary component of the dark current. Controlling the trap concentration to as low as 1×1013 cm-3 will be continuous and meaningful work. The proposed study provides guidance for VLWIR HgCdTe photodetectors.

No effect of thermal maturity on the Mo, U, Cd, and Zn isotope compositions of Lower Jurassic organic-rich sediments

AbstractThe isotope ratios of redox-sensitive metals in organic-rich rocks are critical tools for quantifying the timing and severity of deoxygenation and nutrient cycling in Earth's past. The resilience of isotopic data to thermal alteration of the host sediments over millions of years of burial is, however, largely unknown. We present molybdenum, uranium, cadmium, and zinc stable-isotope data from two stratigraphic successions of the same Lower Jurassic Posidonienschiefer unit in the Lower Saxony Basin of northern Germany that were affected by different burial histories. We show that thermal maturity had no effect on the isotopic compositions of these elements but does appear to have increased their concentrations in the rock. The data corroborate the results of laboratory-based maturation studies and provide constraints on the Mo, U, Cd, and Zn isotopic compositions of ca. 182 Ma seawater in the Lower Saxony Basin.

The Influence of Cd and Ba Incorporation on Microstructure and Photovoltaic Properties in Cu2ZnSnS4 Thin Film

Cd-doping and Ba-doping Cu2ZnSnS4 (CZTS) thin films solar cells were fabricated and compared. Precursors of Cu2ZnSnS4, Cu2(CdZn)SnS4 (CCZTS) and Cu2(BaZn)SnS4 (CBZTS) absorber layer were prepared by the spin coating method and annealed in a powdered sulfur atmosphere. The theoretical Cd or Ba composition was 0.3 according to the element ratio in the solution. The microstructure, morphology, photovoltaic performance of Cd/Ba doping CZTS were analyzed. Ba and Cd oxidation states can be found in the doping samples by XPS. The preferred (112) diffraction peak in CCZTS shifted to low angle apparently due to the increase of the lattice constant with the larger Cd2+ cations. The actual Ba-doping amount was low because Ba alkaline-earth metal easily reacts with H2O in the solution method. Raman spectra showed that the major peaks of CCZTS appeared a red-shift because of Cd-substitution for Zn, while CBZST displayed a blue-shift which could be related to the trigonal structure of CBTS. The stacks structure ZnO/ITO/CdS/CZTS/Mo with Cd/Ba doping solar cells were investigated. Through Cd incorporation the short-circuit current improved from 10.64 to 14.86 mA/cm−2 which is relate to the reduction of the grain boundary defects states, thus achieved conversion efficiency of 3.65%. CBZTS solar cells with Ba incorporation demonstrated the worst performance with inferior short circuit current and open circuit voltage, which originated from optical absorption losses and rough CBZTS/CdS interface with a great deal of recombination centers.

Spatial patterns of Zn, Cd, and Pb isotopic compositions of ground and surface water in mine areas of South Korea reflecting isotopic fractionation during metal attenuation.

As application of multiple metal isotopes can effectively constrain geochemical behavior of contaminants and assess contamination sources and pathways, field-scale studies on the geochemically interlinked fractionation of Zn and Cd isotopes in groundwater are needed. In this study, we collected groundwater samples from multi-level samplers downstream of tailings dumps as well as surface water, ore mineral, precipitate, and tailings samples at the Sambo and Buddeun metallic ore mines in South Korea, and analyzed their Zn, Cd, Pb, and sulfur isotopic compositions. Furthermore, isotopic ratios of ore mineral samples from additional four mines in South Korea (Dangdu, Dongbo, Gomyeong, Samgwang) were compared. A dual isotopic approach using Zn and Cd isotopes was used to assess fractionation processes, and Pb isotopic signatures reflecting their sources were assessed. Increasing trends of δ66Zn and δ114Cd with decreasing Zn and Cd concentrations were observed in groundwater, which was saturated with respect to ZnS (amorphous and sphalerite) and CdS (greenockite). Moreover, for some groundwater samples, δ66Zn showed a positive relationship with δ34SSO4. These results suggest that Zn and Cd are precipitated as sulfide following sulfate reduction. In the plot of δ66Zn against δ114Cd, relatively high and/or increasing δ66Zn in groundwater suggested the effect of fractionation due to sulfide precipitation, while variable and high δ114Cd values suggested the fractionation by adsorption and/or sulfide precipitation, which were based on positive fractionation factors for δ66Zn and δ114Cd during sulfide precipitation and mostly negative and positive fractionation factors for δ66Zn and δ114Cd, respectively, during adsorption. This study shows that the combined use of Zn and Cd isotopes in groundwater can effectively differentiate between adsorption and sulfide precipitation following sulfate reduction in groundwater. Additionally, the 208Pb/206Pb ratios of most water samples reflected those of ore and tailings samples, which verified usefulness of Pb isotopes in water in investigating Pb contamination sources.

Structural, optical, and electrical properties of WZ- and RS-ZnCdO thin films on MgO (100) substrate by molecular beam epitaxy

We have grown the full composition range (0 ≤ x ≤ 1) of Zn1-xCdxO (ZnCdO) thin films on MgO (100) substrates by molecular beam epitaxy. We obtained the wurtzite (WZ) phase in the Cd composition x ≤ 0.51, whereas in the Cd composition x ≥ 0.59, the rocksalt (RS) phase is obtained. A mixed phase of both the WZ and RS phases are observed inside the Cd composition range of 0.59> x >0.51. At this mixed phase region, we observed the WZ phase is transited to RS phase with an increasing band gap energy. We obtained the largest optical band gap energy in WZ-ZnCdO (x = 0) as 3.25 eV and RS-ZnCdO (x = 0.59) as 3.08 eV. In spite of high carrier concentration above 1.3 × 1020 cm−3, low resistivity around 2.5 × 10−4 Ωcm and high mobility of 51.7 cm2/Vs of maximum are observed on RS-ZnCdO thin films.

Search for Double Beta Decay of 106Cd with an Enriched 106CdWO4 Crystal Scintillator in Coincidence with CdWO4 Scintillation Counters

Studies on double beta decay processes in 106Cd were performed by using a cadmium tungstate scintillator enriched in 106Cd at 66% (106CdWO4) with two CdWO4 scintillation counters (with natural Cd composition). No effect was observed in the data that accumulated over 26,033 h. New improved half-life limits were set on the different channels and modes of the 106Cd double beta decay at level of limT1/2∼1020−1022 yr. The limit for the two neutrino electron capture with positron emission in 106Cd to the ground state of 106Pd, T1/22νECβ+≥2.1×1021 yr, was set by the analysis of the 106CdWO4 data in coincidence with the energy release 511 keV in both CdWO4 counters. The sensitivity approaches the theoretical predictions for the decay half-life that are in the range T1/2∼1021−1022 yr. The resonant neutrinoless double-electron capture to the 2718 keV excited state of 106Pd is restricted at the level of T1/20ν2K≥2.9×1021 yr.

Primary study of germanium isotope composition in sphalerite from the Fule Pb–Zn deposit, Yunnan province

The Sichuan–Yunnan–Guizhou metallogenic province in southwest China is one of the most important low-temperature metallogenic domains in the country, and more than 400 Pb–Zn deposits and/or mineralization points are located in this area. The Fule deposit is better known that the other Pb–Zn deposits in the region because it is extremely highly enriched with dispersed elements, including Ge, Ga, and Cd. Based on information obtained from our previous studies, the contents of Ge and its isotopic compositions in sphalerite are investigated herein. Results show that the Ge content ranges from 60 ppm to 141.5 ppm, and δ74/70Ge values vary from −6.57‰ to 0.97‰. In this respect, −6.57‰ is the most negative Ge isotope composition value reported in any sphalerite or seafloor sulfides to date. The Cd and Ge contents in sphalerite have a good negative relationship, and it is suggested that the mechanisms of Cd and Zn substitution are responsible for the low incorporation of Ge and relate to the high Cd content (up to 3%) of the sphalerite. In addition, there is a good positive correlation between the Ge contents and δ34S values, which was likely triggered by variations of fluid temperature. In the same hand specimen, light Ge isotope is more likely to be enriched in dark sphalerite rather than light sphalerite, similarly to Cd isotope distribution in dark and light-colored sphalerite. In addition, Cd and Ge isotope compositions, measured in an ore profile from SBFL22 to SBFL26, show a good positive relationship, suggesting that the fractionation mechanisms between Cd and Ge isotopes may be similar and they were controlled by kinetic fractionation during sphalerite precipitation. Based upon previous limited studies, we conclude that Ge in the Fule deposit is derived from mixing sources and sediment is likely the dominant one.

Low-Frequency Noise Spectroscopy Characterization of HgCdTe Infrared Detectors

Low-frequency noise spectroscopy (LFNS) is an effective tool to study the trap properties in infrared photodetectors which may cause the limitations of dark current, dark noise, and quantum efficiency as well. In this article, the trap levels of HgCdTe infrared detectors with different Cd compositions are investigated with LFNS. The defect levels within the bandgap have been identified. In addition, trap states with activation energy above the material bandgap are also found for Hg-vacancy doped mid-wavelength and long-wavelength infrared HgCdTe photodetectors due to the resonant states located above the conduction band edge. The method to eliminate these resonant states is also investigated.

CuZn2InTe4 quantum dots-a novel nanostructure employing a green synthesis route.

We report the synthesis and characterisation of novel CuZn2InTe4 quantum dots (QDs) suitable for various optoelectronic applications. The nanostructures grown are technologically important due to their Cd and Pb-free composition. The synthesis was maintained “green” by using a phosphine free organometallic procedure utilizing octadecene as the coordinating solvent. The structural properties of the nanocrystals (NCs) were analyzed using high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED) and X-ray diffraction (XRD). The composition was verified using X-ray photoelectron spectroscopy (XPS), inductive coupled plasma-optical emission spectroscopy (ICP-OES) and energy dispersive X-ray spectroscopy (EDX). The optical studies were performed using UV-VIS-NIR spectroscopy and photoluminescence (PL) spectroscopy and the band gap value obtained was verified using cyclic voltammetry (CV). The nanostructures grown were spherical with a size of about 5 nm possessing appreciable monodispersity.

Effects of oxygen stoichiometry on the phase stability of sputter-deposited CdxZn1−xO alloys

The phase transition and stability as well as corresponding electrical and optical properties of $\mathrm{C}{\mathrm{d}}_{x}\mathrm{Z}{\mathrm{n}}_{1\ensuremath{-}x}\mathrm{O}$ alloys over the entire composition range synthesized under different sputtering conditions, namely, substrate temperature and sputtering environment, were studied. We found that the composition at which the phase transition from the wurtzite (WZ) ZnO-like to rocksalt (RS) CdO-like phase occurs critically depends on the growth temperature and environment during sputter deposition. When deposited at room temperature in pure Ar, the composition window for the coexistence of both the WZ and RS phases is rather narrow ($0.62lxl0.7$). This mixed phase window widens considerably to $0.4lxl0.7$ when alloys were synthesized at $230{\phantom{\rule{0.28em}{0ex}}}^{\ensuremath{\circ}}\mathrm{C}$. When grown in an O-rich environment, pure WZ alloys are stable up to a much higher Cd composition of $x\ensuremath{\sim}0.72$ with a narrow mixed phase region $(0.72lxl0.8)$, resulting in oxide alloys with band gap in the visible range ($\ensuremath{\sim}1.8\phantom{\rule{0.16em}{0ex}}\mathrm{eV}$ for $x\ensuremath{\sim}0.7$). The enhanced WZ phase stability agrees with density functional theory calculations by considering the incorporation of extra O as interstitial defects. Since the optical and electrical transport properties of CdZnO alloys in the WZ and RS phases differ drastically, by adjusting the growth conditions, alloys with desired properties (e.g., band gap and conductivity) can be achieved for different optoelectronic applications.