Te Flux Research Articles

Linking the PETM and North Atlantic volcanism using tellurium in sediments

The Paleocene – Eocene Thermal Maximum (PETM) was a short period (~170 kyr) of global temperature rise starting at 55.93 Ma, which occurred during the breakup of the North Atlantic and the emplacement of the North Atlantic Igneous Province (NAIP). Recently, mercury (Hg) concentrations in sediments have been used in an attempt to connect the eruptive history of the NAIP with environmental change during this period, at a higher resolution than possible using geochronology. Here we present sedimentary tellurium (Te) as a novel proxy to further reconstruct NAIP volcanism at high resolution. We measured 45 trace elements in 401 sediment samples from 3 sections across the PETM in the northern hemisphere. All study sites exhibit an increase in Te concentrations and Te/Th ratios close to the onset of the PETM and remain high until the end of the main North Atlantic ash phase about 1 Myr later. The trace element data indicate that changes in sediment lithology or in environmental conditions do not influence sedimentary Te concentrations suggesting a volcanic source instead. We used existing age models to remove the effect of changes in sedimentation rate and calculated volcanic Te fluxes. Our Te data suggest increased volcanism in the latest Paleocene and early Eocene. This fits existing radiometric ages of the NAIP, which demonstrate that a more than 5 km thickness of lava in eastern Greenland and the Faroes was erupted within about 1 Myr between ~56 to ~55 Ma. All our study sites show similar Te flux variations across the PETM. In contrast, sedimentary mercury (Hg) profiles from these and other sites are less consistent. Tellurium in sediments may represent a useful proxy to reconstruct NAIP volcanism.

Reversed-direction 2-point modelling applied to divertor conditions in DIII-D *

A predictive form of the extended 2-point model known as the ‘reverse 2-point model’, Rev2PM, is applied to a range of detachment levels in the open lower divertor of DIII-D, showing that the experimentally measured electron temperature (Te ) and pressure (pe ) at the divertor entrance can be calculated within 50% from target measurements, if and only if a posteriori corrections for convective heat flux are included in the model. Unlike the standard 2-point model, the Rev2PM calculates upstream scrape-off layer (SOL) quantities (such as separatrix Te and pe ) from target conditions (such as Te and parallel heat flux), with volumetric power and momentum losses depending solely on target Te . The Rev2PM is tested against a database of DIII-D inter-ELM divertor Thomson scattering measurements, built from a series of 6 MW, 1.3 MA, LSN H-mode discharges with varied main ion density, drift direction, and nitrogen puffing rate. Measured target Te ranged from 0.4–25 eV over this database, and upstream Te ranged from 5–60 eV. Poor agreement is found between upstream measurements and Rev2PM calculations that assume purely conductive parallel heat transport. However, introducing a posteriori corrections to account for convective heat transport brings the Rev2PM calculations within 50% of the measured upstream values across the dataset. These corrections imply that up to 99% of the parallel heat flux is carried by convection in detached conditions in the DIII-D open lower divertor, though further work is required to assess any potential dependencies on device size or divertor closure.

In-plane mixed-dimensional 2D/2D/1D MoS2/MoTe2/Mo6Te6 heterostructures for low contact resistance optoelectronics

Mixed-dimensional heterostructures formed by combining 2D materials and other dimensional (0D, 1D, and 3D) materials provide new opportunities for various applications owing to their novel properties. However, in-plane mixed-dimensional heterostructures have been rarely investigated. Here, we report a novel flux-controlled chemical vapor deposition method for synthesizing in-plane mixed-dimensional heterostructures composed of monolayer MoS2 and low-dimensional Mo/Te compounds. By adjusting the Te flux and growth time, we controlled the composition, dimension, and phase of the Mo/Te compounds interfaced with the MoS2. While in-plane 2D/1D MoS2/Mo6Te6 and 2D/2D/1D MoS2/2H MoTe2/Mo6Te6 heterostructures were obtained with a low Te flux, in-plane 2D/2D MoS2/mixed 2H-1T’ MoTe2 and 2D/2D MoS2/2H MoTe2 heterostructures were synthesized with a high Te flux. We investigated the transport properties of the devices fabricated with in-plane mixed-dimensional 2D/2D/1D MoS2/2H MoTe2/Mo6Te6 heterostructures and imaged localized electronic band structures using scanning photocurrent microscopy. Under the low bias condition, the device exhibited an Ohmic-like behavior, which has not been achieved in conventional devices with stacked van der Waals junctions. Under the high bias condition, the device showed a rectifying behavior because of band-bending formed at the heterojunctions; this is consistent with the electronic band-alignment expected from the bandgap and electron affinity of the materials.

Growth of ZnTe Semiconductor Crystal Via a Te Flux Zone Melting Method and Characterization of Its Properties

AbstractIn this work, a kind of II;‐VI group ZnTe semiconductor crystal is successfully grown using a Te flux zone melting method from Zn: Te = 3: 7 mole ratio solution. The crystal has standard F43m cubic space group and the a/b/c lattice constants are all calculated to be 6.105 Å. Energy dispersive spectroscopy analysis confirms it has quasistoichiometric ratio and the Zn/Te elements are distributed in the material homogeneously. The polished 1.0 mm thickness (110) wafer exhibits a highest ≈64.5% transmittance near 2400 nm wavelength and the bandgap Eg is deduced as 2.223 eV. ZnTe crystal shows a heavy volatilization start from 910 °C and the weight losing speed is about ≈1.45% min−1. The thermal conductivity k displays good repeatability in the cooling and heating stages, the k value is about 15.8 Wm−1 K−1 at room temperature and is deceased to 3.53 Wm−1 K−1 under 500 °C. These results would be of great reference when ZnTe crystal is used for device design and application in the future.

Epitaxial growth, intrinsic point defects and electronic transport optimization of MnTe films

The NiAs-type MnTe compound is one of important and environmental friendly p-type thermoelectric materials for generating intermediate temperature powern. The low hole concentration in the pristine MnTe greatly restricts its thermoelectric performance. However, the systematic experimental studies of thermoelectric materials are still lacking so far. In this work, MnTe thin films are grown by molecular beam epitaxy (MBE) technique, and their intrinsic point defect structures are characterized by scanning tunneling microscope (STM). Through the regulation of the intrinsic point defects, the electrical transport performances of MnTe films are remarkably improved. The results show that Mn vacancies (V<sub>Mn</sub>) and Te vacancies (V<sub>Te</sub>) are the dominant intrinsic point defects in MnTe film. With the increase of the substrate temperature (<i>T</i><sub>sub</sub>) and the decrease of the Mn:Te flux ratio, the hole concentration in MnTe film increases greatly, reaching a maximum value of 21.5 × 10<sup>19</sup> cm<sup>–3</sup>, which is one order of magnitude higher than that of the intrinsic MnTe bulk. This is attributed to the significantly increased concentration of p-type V<sub>Mn</sub> in MnTe film, and thus leads the conductivity (<i>σ</i>) and power factor (<i>PF</i>) to increase remarkably. Finally, the MnTe film grown at <i>T</i><sub>sub</sub> = 280 ℃ and Mn∶Te = 1∶12 obtains the maximum <i>PF</i> of 1.3 μW·cm<sup>–1</sup>·K<sup>–2</sup> at 483 K in all grown films. This study clarifies the characteristics of intrinsic point defects and their relationship with the electrical transport properties of MnTe based compounds, which provides an importantguidance for further optimizing their thermoelectric performances.

Tunable and Robust Near-Room-Temperature Intrinsic Ferromagnetism of a van der Waals Layered Cr-Doped 2H-MoTe2 Semiconductor with an Out-of-Plane Anisotropy.

The intrinsically nonmagnetic feature of van der Waals (vdW) layered transition-metal dichalcogenide (TMDC) semiconductors limits the spintronic applications of these semiconductors. In this paper, we demonstrate a facile Te flux strategy to induce intrinsic ferromagnetism in the vdW layered 2H-MoTe2 semiconductor by magnetic chromium (Cr) doping. The Curie temperature (Tc) and saturation magnetization (Ms) can be well tuned by adjusting the Cr doping concentration. A notable Tc up to 275 K can be achieved for the vdW layered Cr-doped 2H-MoTe2 bulk crystals, which is much higher than that of recently reported van der Waals ferromagnetic semiconductors (Tc is mostly less than 70 K), in contrast to the diamagnetic feature of the pristine MoTe2. Meanwhile, the highest Ms of the vdW layered Cr-doped 2H-MoTe2 bulk crystals can reach 4.78 emu g-1, which is stronger than most values reported for magnetic-element-doped van der Waals materials. In addition, all of the as-grown semiconducting Cr-doped 2H-MoTe2 (Cr-2H-MoTe2) single crystals display a large magnetic anisotropy with an out-of-plane easy axis of magnetization. The observed ferromagnetism in the Cr-2H-MoTe2 has intrinsic characteristics, which can be mainly attributed to the spin polarization caused by Cr doping as confirmed by the density functional theory (DFT) calculations. Our approach offers an avenue to tune the ferromagnetism in the vdW layered semiconductor and explore its diverse spintronic and magnetoelectric applications.

Highly Tunable Near‐Room Temperature Ferromagnetism in Cr‐Doped Layered Td‐WTe2

AbstractThe discovery of type‐II Weyl semimetal states in layered transition metal dichalcogenides Td‐WTe2 indicates great potential for novel electronic, spintronic, and quantum devices. Theoretically, the interaction between the topological states and the magnetic ordered states of Td‐WTe2 enables the modulation of Weyl semimetal states by an external magnetic field. However, currently, ferromagnetism in layered Td‐WTe2 is still elusive and rarely observed. In this research, ferromagnetic order into WTe2 using magnetic chromium (Cr) doping with a two‐step Te flux strategy is introduced. The Curie temperature (Tc) and the ferromagnetic moment are well tuned with a Cr doping concentration. The Tc of the Cr‐doped layered Td‐WTe2 could be regulated from 182 to 283 K, which is close to room temperature. The saturation magnetic moment could be changed from 2.26 to 4.20 emu g–1, which is stronger than most values reported for these materials. Most intriguingly, the Cr‐doped layered Td‐WTe2 single crystals still exhibit semimetallic behavior and they possess very large magnetoresistance with obvious Shubnikov de Haas (SdH) quantum oscillations and an anomalous Hall effect. The findings offer feasible ways to induce and tune ferromagnetic orders in layered Td‐WTe2 and thus to control its topological phase with external magnetic fields.

Mixed-Dimensional In-Plane Heterostructures from 1D Mo6 Te6 and 2D MoTe2 Synthesized by Te-Flux-Controlled Chemical Vapor Deposition.

Mixed-dimensional van der Waals heterostructures are scientifically important and practically useful because of their interesting exotic properties resulting from their novel hybrid structures. This study reports the composition- and phase-selective fabrication of low-dimensional molybdenum/tellurium (Mo/Te) compounds and the direct synthesis of mixed-dimensional in-plane 1D-2D Mo6 Te6 -MoTe2 heterostructures. The composition and phase of the Mo/Te compounds are controlled by changing the Te atomic flux that is adjusted by the Te temperature. Metallic 1D Mo6 Te6 wires with an intrinsic 1D structure with a diameter of 3-8nm and length of 100-300nm are synthesized to form wire networks under low Te flux conditions, whereas the semiconducting few-layer 2H MoTe2 films preferentially oriented along the <0001>direction are obtained under high Te flux. Under medium Te flux, the mixed-dimensional in-plane 1D-2D Mo6 Te6 -MoTe2 heterostructures are synthesized in which the semiconducting few-layer 2H MoTe2 circular domains are edge-contacted by the metallic 1D Mo6 Te6 wire networks. Furthermore, the present Te-flux-controlled method reveals that the 1D Mo6 Te6 networks change to few-layer MoTe2 films as the Te flux increases. The in-plane 1D-2D Mo6 Te6 -MoTe2 heterostructures synthesized by this method can be considered as advanced edge-contacted 2D semiconductors for high-performance 2D electronics.

Growth and characterization of ZnTe single crystal via a novel Te flux vertical Bridgman method

In this work, an II–VI group semiconductor zinc telluride (ZnTe) single crystal is prepared by a novel vertical Bridgman method using Te as flux. The initial mole ratio of Zn/Te = 3:7 is designed for raw material synthesis. ZnTe polycrystalline combined with rich Te is effectively fabricated through rocking technique at 1100 °C. A Φ 25 mm × 65 mm ZnTe boule is successfully grown under a ~ 40 °C·cm−1 temperature gradient with a growth speed of 5 mm·day−1. The as-grown ZnTe crystal has a standard 1:1 stoichiometric ratio and pure F43m phase structure. The maximum transmittance perpendicular to (110) plane is about 64%, and the band gap (Eg) is tested to be 2.225 eV. Terahertz (THz) examination results demonstrate that the time of the highest THz signal is around 17 ps and the frequency of the highest THz transmission is about 0.78 THz, implying that the ZnTe crystal grown by the present Te flux vertical Bridgman method has a good feasibility for THz application.

Bulk Fermi surfaces of the Dirac type-II semimetallic candidate NiTe2

Here, we present a study on the Fermi-surface of the Dirac type-II semi-metallic candidate NiTe$_2$ via the temperature and angular dependence of the de Haas-van Alphen (dHvA) effect measured in single-crystals grown through Te flux. In contrast to its isostructural compounds like PtSe$_2$, band structure calculations predict NiTe$_2$ to display a tilted Dirac node very close to its Fermi level that is located along the $\Gamma$ to A high symmetry direction within its first Brillouin zone (FBZ). The angular dependence of the dHvA frequencies is found to be in agreement with the first-principle calculations when the electronic bands are slightly shifted with respect to the Fermi level ($\varepsilon_F$), and therefore provide support for the existence of a Dirac type-II node in NiTe$_2$. Nevertheless, we observed mild disagreements between experimental observations and density Functional theory calculations as, for example, nearly isotropic and light experimental effective masses. This indicates that the dispersion of the bands is not well captured by DFT. Despite the coexistence of Dirac-like fermions with topologically trivial carriers, samples of the highest quality display an anomalous and large, either linear or sub-linear magnetoresistivity. This suggests that Lorentz invariance breaking Dirac-like quasiparticles dominate the carrier transport in this compound.

Growth of large scale PtTe, PtTe2 and PtSe2 films on a wide range of substrates

1T phase of transition metal dichalcogenides (TMDCs) formed by group 10 transition metals (e.g. Pt, Pd) have attracted increasing interests due to their novel properties and potential device applications. Synthesis of large scale thin films with controlled phase is critical especially considering that these materials have relatively strong interlayer interaction and are difficult to exfoliate. Here we report the growth of centimeter-scale PtTe, 1T-PtTe2 and 1T-PtSe2 films via direct deposition of Pt metals followed by tellurization or selenization. We find that by controlling the Te flux, a hitherto-unexplored PtTe phase can also be obtained, which can be further tuned into PtTe2 by high temperature annealing under Te flux. These films with different thickness can be grown on a wide range of substrates, including NaCl which can be further dissolved to obtain free-standing PtTe2 or PtSe2 films. Moreover, a systematic thickness dependent resistivity and Hall conductivity measurements show that distinguished from the semiconducting PtSe2 with hole carriers, PtTe2 and PtTe films are metallic. Our work opens new opportunities for investigating the physical properties and potential applications of group 10 TMDC films and the new monochalcogenide PtTe film.

Results of Ion Cyclotron Heating Experiments on Proto-MPEX Utilizing a Movable Stainless Steel Target

Ion cyclotron heating (ICH) at a frequency in the 6- to 9-MHz range with electron heating in the 28- to 105-GHz range will be used in the Material Plasma Exposure eXperiment (MPEX) to greatly increase the energy of the plasma stream produced by the helicon plasma source. ICH was chosen over substrate biasing to produce energetic ions because it can more accurately reproduce plasma-material interactions in a fusion device. For instance, when the target is tilted with respect to the background magnetic field during ICH, a magnetic presheath is created so that redeposition phenomena as in a tokamak divertor can be better approximated. ICH experiments were conducted on the Proto-MPEX device, which was developed to provide a physics basis upon which MPEX is designed. In this paper we describe some of these experiments in which the previous fixed graphite target was replaced by a movable stainless steel target. With the new target, the strong, monotonic decrease in ion temperature observed previously as a function of axial distance between the ion cyclotron resonance region and the target was not observed. Instead, only a small drop was seen within ~1 cm of the target. The ion temperatures were determined spectroscopically, utilizing Doppler broadening measurements of an Ar II line, in a plasma that is 90% deuterium and 10% argon. Measurements were obtained using optical fibers at a fixed location, with the target moving perpendicularly relative to the viewing chords. Comparisons with previous results will be discussed, including observed plasma parameters Ti, Te, and ne, and heat flux at the target.

Influence of Surface Structures on Quality of CdTe(100) Thin Films Grown on GaAs(100) Substrates**Supported by the National Key Research and Development Program of China under Grant Nos 2017YFB0405704 and 2017YFA0305400, the 1000-Young Talent Program of China, and the Shanghai Sailing Program under Grant No 17YF1429200.

We report the epitaxial growth of single-crystalline CdTe(100) thin films on GaAs(100) substrates using molecular beam epitaxy. By controlling the substrate pre-heated temperature with adjustable Te flux, three different reconstructed surfaces are realized, and their influence on the subsequent CdTe growth is investigated. More importantly, we find that both the presence of a thin native oxide layer and the formation of Ga-As-Te bonds at the interface enable the growth along the (100) orientation and help to reduce the threading dislocations and other defects. Our results provide new opportunities for compound semiconductor heterogeneous growth via interfacial engineering.

Bulk Fermi surface of the Weyl type-II semimetallic candidate γ−MoTe2

The electronic structure of WTe$_2$ and orthorhombic $\gamma-$MoTe$_2$, are claimed to contain pairs of Weyl type-II points. A series of ARPES experiments claim a broad agreement with these predictions. We synthesized single-crystals of MoTe$_2$ through a Te flux method to validate these predictions through measurements of its bulk Fermi surface (FS) \emph{via} quantum oscillatory phenomena. We find that the superconducting transition temperature of $\gamma-$MoTe$_2$ depends on disorder as quantified by the ratio between the room- and low-temperature resistivities, suggesting the possibility of an unconventional superconducting pairing symmetry. Similarly to WTe$_2$, the magnetoresistivity of $\gamma-$MoTe$_2$ does not saturate at high magnetic fields and can easily surpass $10^{6}$ \%. Remarkably, the analysis of the de Haas-van Alphen (dHvA) signal superimposed onto the magnetic torque, indicates that the geometry of its FS is markedly distinct from the calculated one. The dHvA signal also reveals that the FS is affected by the Zeeman-effect precluding the extraction of the Berry-phase. A direct comparison between the previous ARPES studies and density-functional-theory (DFT) calculations reveals a disagreement in the position of the valence bands relative to the Fermi level $\varepsilon_F$. Here, we show that a shift of the DFT valence bands relative to $\varepsilon_F$, in order to match the ARPES observations, and of the DFT electron bands to explain some of the observed dHvA frequencies, leads to a good agreement between the calculations and the angular dependence of the FS cross-sectional areas observed experimentally. However, this relative displacement between electron- and hole-bands eliminates their crossings and, therefore, the Weyl type-II points predicted for $\gamma-$MoTe$_2$.

In-Plane 2H-1T' MoTe2 Homojunctions Synthesized by Flux-Controlled Phase Engineering.

The fabrication of in-plane 2H-1T' MoTe2 homojunctions by the flux-controlled, phase-engineering of few-layer MoTe2 from Mo nanoislands is reported. The phase of few-layer MoTe2 is controlled by simply changing Te atomic flux controlled by the temperature of the reaction vessel. Few-layer 2H MoTe2 is formed with high Te flux, while few-layer 1T' MoTe2 is obtained with low Te flux. With medium flux, few-layer in-plane 2H-1T' MoTe2 homojunctions are synthesized. As-synthesized MoTe2 is characterized by Raman spectroscopy and X-ray photoelectron spectroscopy. Kelvin probe force microscopy and Raman mapping confirm that in-plane 2H-1T' MoTe2 homojunctions have abrupt interfaces between 2H and 1T' MoTe2 domains, possessing a potential difference of about 100 mV. It is further shown that this method can be extended to create patterned metal-semiconductor junctions in MoTe2 in a two-step lithographic synthesis. The flux-controlled phase engineering method could be utilized for the large-scale controlled fabrication of 2D metal-semiconductor junctions for next-generation electronic and optoelectronic devices.

Structural and magnetic properties of (Zn,Fe)Te thin films grown by MBE under Zn-rich flux condition

We have performed the structural and magnetic characterization of Zn1-xFexTe thin films grown by molecular beam epitaxy (MBE). Thin films of Zn1-xFexTe with Fe composition up to x~0.06 were grown by MBE with the supply of excess Zn flux over Te flux. From the structural analyses by x-ray absorption fine structure (XAFS), it is revealed that the grown film with a low Fe content x=0.015 is composed of pure diluted phase with substitutional Fe atoms while the precipitation of an extrinsic phase is suggested at higher Fe contents x=0.03~0.06. The magnetization measurement reveals a clear distinction in the magnetic-field (M-H) and temperature (M-T) dependences between the low and high Fe contents; a hysteretic M-H dependence and the blocking phenomenon in the M-T dependence at the higher Fe content. These behaviors are attributed to the superparamagnetism, originating from the formation of an extrinsic precipitate.

Heterostructures with CdTe/ZnTe quantum dots for single photon emitters grown by molecular beam epitaxy

We report on the molecular beam epitaxy (MBE) of heterostructures with CdTe/ZnTe quantum dots (QDs) with relatively low surface density, which could be used as single-photon emitters. The QDs were formed on the surface of a 3.1- to 4.5-monolayer-thick two-dimensional strained CdTe layer by depositing amorphous Te layer and its fast thermal desorption. Subsequent thermal annealing of the surface with QDs in the absence of external Te flux led to strong broadening and short-wavelength shift of the QD photoluminescence (PL) peak. Measurement of the micro-PL spectra of individual CdTe/ZnTe quantum dots in fabricated mesastructures with a diameter of 200—1000 nm allowed estimation of the QD surface density as ~1010 cm–2.

Selective growth of ZnTe on sapphire substrates using a SiO2 mask

ZnTe/sapphire heterostructures have attracted attention for their suitable properties as a terahertz wave detector material. In this study, we focused on the selective growth of ZnTe on SiO2‐masked sapphire substrates by molecular beam epitaxy (MBE). When ZnTe was grown at a high temperature (=350 °C), low growth rate (≦ 0.3 μm h−1), and low JTe/JZn flux ratio (≦ 0.83) compared with the conventional film growth conditions, the formation of ZnTe nuclei on the SiO2 mask was avoided. The Te flux intensity significantly affected the selectivity of ZnTe growth. The selective growth of ZnTe on sapphire was revealed to be limited by the desorption of Te adatoms from the SiO2.

Study of optimization options for second generation solar cell materials by multilevel modeling

Theoretical analysis of optimization options for the properties of CdTe absorber layer is an important task for increasing the efficiency of CdTe/CdS heterojunction based thin-film solar cells. Properties of the materials (e.g. the density of free carriers) often depend essentially on the parameters of the deposition process and subsequent treatment which determine the defect composition of the material. In this work a model based on the lattice kinetic Monte-Carlo method is developed to describe the process of CdTe deposition as a function of temperature and Cd and Te fluxes. To determine the effect of the treatment conditions on CdTe conductivity, we developed a quasichemical model based on the electrical neutrality equation for point defect concentrations that are described by defect formation reaction constants. Parameters obtained from the first-principles density functional calculations were used for developing the models. The developed deposition model correctly describes the transition from evaporation to precipitation as well as the increased evaporation rates in excess of Cd. To explain the observed electrical properties of CdTe after Cl-treatment, we complemented the quasichemical defect model by a deep acceptor complex defect that allowed us to describe both the high-temperature dependence of conductivity on the Cd pressure and the dependence of resistivity on Cl concentration at room temperature.

Stoichiometry dependence of the optical and minority-carrier lifetime behaviors of CdTe epitaxial films: A low-temperature and time-resolved photoluminescence study

Cadmium telluride (CdTe) epitaxial films (EFs) were grown on near-lattice-matched Cd0.96Zn0.04Te (CZT) substrates by molecular beam epitaxy at different ambients to achieve Cd-rich samples with extra Cd molecular flux or Te-rich samples with extra Te molecular flux. The evolution of epitaxial growth was in situ monitored by reflection high-energy electron diffraction (RHEED). A two-dimensional growth mode was indicated by the streaky RHEED patterns. Crystal structures of the CdTe EFs were characterised by X-ray diffraction (XRD). XRD data suggested that the crystal quality of the CdTe EFs was improved by controlling the Cd and Te flux ratio. Low-temperature photoluminescence (PL) spectra were carried out in these CdTe EFs. The typical characteristic peak at ∼1.552eV denoted as the bound-to-free transition was only found in CdTe samples grown under an extra Cd flux, and Cd vacancy-related defects were absent in the Cd-rich EFs, confirming the Cd-rich or Te-rich states of the epitaxial CdTe films. Finally, minority-carrier lifetime was prolonged in Cd-rich CdTe EFs as supported by time-resolved photoluminescence (TRPL) measurement.