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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Phosphoric Acid-Doped Ion-Pair Coordinated PEMs with Broad Relative Humidity Tolerance

Proton exchange membrane (PEM) capable of working over a broad operating condition window is critical for successful adoption of PEM-based electrochemical devices. In this work, phosphoric acid (PA)-doped biphenyl-backbone ion-pair coordinated PEMs were prepared by quaternization of BPBr-100, a precursor polymer, with three different tertiary amines including trimethylamine, 1-methylpiperidine, and 1,2-dimethylimidazole followed by membrane casting, ion exchange reaction to hydroxide ion, and doping with PA. The resulting PA-doped ion-pair PEMs were characterized in terms of PA doping level, proton conductivity, relative humidity (RH) tolerance, thermal stability, and mechanical properties. PA doping levels were between six and eight according to acid-base titration. The size and structure of the cation group of ion-pair polymers were found to affect the PA doping level and water uptake. Proton conductivity was studied as a function of RH over a wide range of 5% to 95% RH. Stable conductivity at 80 °C was observed up to 70% RH for 10 h. Mechanical property characterization indicates that the PA doping process resulted in more ductile membranes with significantly increased elongation at break due to the plasticization effect of PA. A combination of high proton conductivity at low RH conditions, and good humidity tolerance makes this new class of PEMs great potential candidates for use in electrochemical devices such as proton exchange membrane fuel cells and electrochemical hydrogen compressors.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Sequential Doping of Ladder-Type Conjugated Polymers for Thermally Stable n-Type Organic Conductors

Doping of organic semiconductors is a powerful tool to optimize the performance of various organic (opto)electronic and bioelectronic devices. Despite recent advances, the low thermal stability of the electronic properties of doped polymers still represents a significant obstacle to implementing these materials into practical applications. Hence, the development of conducting doped polymers with excellent long-term stability at elevated temperatures is highly desirable. Here, we report on the sequential doping of the ladder-type polymer poly(benzimidazobenzophenanthroline) (BBL) with a benzimidazole-based dopant (i.e., N-DMBI). By combining electrical, UV–vis/infrared, X-ray diffraction, and electron paramagnetic resonance measurements, we quantitatively characterized the conductivity, Seebeck coefficient, spin density, and microstructure of the sequentially doped polymer films as a function of the thermal annealing temperature. Importantly, we observed that the electrical conductivity of N-DMBI-doped BBL remains unchanged even after 20 h of heating at 190 °C. This finding is remarkable and of particular interest for organic thermoelectrics.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Cobalt‐Doped Bismuth Nanosheet Catalyst for Enhanced Electrochemical CO 2 Reduction to Electrolyte‐Free Formic Acid

Electrochemical carbon dioxide (CO 2 ) reduction reaction (CO 2 RR) to valuable liquid fuels, such as formic acid/formate (HCOOH/HCOO − ) is a promising strategy for carbon neutrality. Enhancing CO 2 RR activity while retaining high selectivity is critical for commercialization. To address this, we developed metal-doped bismuth (Bi) nanosheets via a facile hydrolysis method. These doped nanosheets efficiently generated high-purity HCOOH using a porous solid electrolyte (PSE) layer. Among the evaluated metal-doped Bi catalysts, Co-doped Bi demonstrated improved CO 2 RR performance compared to pristine Bi, achieving ~90 % HCOO − selectivity and boosted activity with a low overpotential of ~1.0 V at a current density of 200 mA cm −2 . In a solid electrolyte reactor, Co-doped Bi maintained HCOOH Faradaic efficiency of ~72 % after a 100-hour operation under a current density of 100 mA cm −2 , generating 0.1 M HCOOH at 3.2 V. Density functional theory (DFT) results revealed that Co-doped Bi required a lower applied potential for HCOOH generation from CO 2 , due to stronger binding energy to the key intermediates OCHO* compared to pure Bi. In conclusion, this study shows that metal doping in Bi nanosheets modifies the chemical composition, element distribution, and morphology, improving CO 2 RR catalytic activity performance by tuning surface adsorption affinity and reactivity.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Magnetic and transport properties of Fe-doped Weyl semimetal Co 3 Sn 2 S 2

Ferromagnetic Weyl semimetal Co 3 Sn 2 S 2 has recently attracted a lot of interest on account of its large non-saturating magnetoresistance and the high carrier mobility common to topological semimetals. Moreover, the material also provides a platform for studying the interplay between the intrinsic magnetism and topological band structures, which generates a significant anomalous Hall effect. Chemical doping is the usual approach to adjust materials’ properties, and it can lead to fascinating results. Here, we present the influence of Fe-doping on the magnetic and transport properties of polycrystalline Co 3 Sn 2 S 2 . The Fe-doping suppresses the sample’s magnetic order, increases the electrical resistivity, results in a skew-scattering contribution to the anomalous Hall effect and Fe impurities cause the Kondo effect. In addition, we report on the impact of Fe-doping on the magnetoresistance of Co 3 Sn 2 S 2 , where Fe-doping leads to a dramatic decline in magnetoresistance. Furthermore, the hysteresis behavior in the low magnetic field region, detected previously in nanoflake samples only, is observed in both pure and Fe-doped Co 3 Sn 2 S 2 bulk samples. Finally, our findings serve as a reference and source of inspiration for future chemical doping research on topological semimetals.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Tuning Thermal Stability through Dopant Size in Chemically Doped DPP–Thiophene Polymers

Molecular doping of conjugated polymers (CPs) is a key strategy for improving the performance of organic electronics devices, particularly thermoelectrics. Doped donor–acceptor (D–A) conjugated polymers, characterized by a tunable energy gap between the Fermi level and the transport band, show great promise in achieving high electrical conductivity (σ) while preserving a favorable Seebeck coefficient (S). Despite the promising performance enhancement of chemically doped D–A polymers, their thermal stability remains largely underexplored, a crucial consideration for the long-term operation of organic thermoelectric devices. In this study, we investigated the dopant size-dependent thermal stability of a diketopyrrolopyrrole-thiophene (DPP-T) D–A copolymer, utilizing two p-dopants: 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F 4 TCNQ) and Mo(tfd-CO 2 Me) 3 . Temperature-dependent UV–vis–NIR spectroscopy revealed that DPP-T/F 4 TCNQ is more prone to dedoping under a high temperature thermal stress than DPP-T/Mo(tfd-CO 2 Me) 3 . Although the F 4 TCNQ doped polymer shows higher initial in-plane conductivity than its Mo(tfd-CO 2 Me) 3 counterpart, it undergoes a conductivity loss of more than an order of magnitude after annealing at 120 °C for 30 min. In contrast, the in-plane conductivity of DPP-T/Mo(tfd-CO 2 Me) 3 remains stable under the same thermal conditions. Thermogravimetric analysis ruled out dopant sublimation as a primary contributor to dedoping, leading us to attribute the conductivity loss in F 4 TCNQ-doped DPP-T to dopant phase separation and migration. This observation was further confirmed by X-ray scattering studies and nanoscale infrared microscopy and spectroscopy studies. This work could provide further insights into the thermal stability of doped conjugated polymers and suggests that incorporating bulkier dopants is an effective strategy to enhance the thermal robustness of doped DPP-type systems.

Conjugated polymers↗
DOE OSTI2020

Reversible writing of high-mobility and high-carrier-density doping patterns in two-dimensional van der Waals heterostructures

A key feature of two-dimensional materials is that the sign and concentration of their carriers can be externally controlled with techniques such as electrostatic gating. However, conventional electrostatic gating has limitations, including a maximum carrier density set by the dielectric breakdown, and ionic liquid gating and direct chemical doping also suffer from drawbacks. In this work, we show that an electron-beam-induced doping technique can be used to reversibly write high-resolution doping patterns in hexagonal boron nitride-encapsulated graphene and molybdenum disulfide (MoS 2 ) van der Waals heterostructures. The doped MoS 2 device exhibits an order of magnitude decrease of subthreshold swing compared with the device before doping, whereas the doped graphene devices demonstrate a previously inaccessible regime of high carrier concentration and high mobility, even at room temperature. We also show that the approach can be used to write high-quality p–n junctions and nanoscale doping patterns, illustrating that the technique can create nanoscale circuitry in van der Waals heterostructures.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Emergence of quasiparticles in a doped Mott insulator

How a Mott insulator develops into a weakly coupled metal upon doping is a central question to understanding various emergent correlated phenomena. To analyze this evolution and its connection to the high- T c cuprates, we study the single-particle spectrum for the doped Hubbard model using cluster perturbation theory on superclusters. Starting from extremely low doping, we identify a heavily renormalized quasiparticle dispersion that immediately develops across the Fermi level, and a weakening polaronic side band at higher binding energy. The quasiparticle spectral weight roughly grows at twice the rate of doping in the low doping regime, but this rate is halved at optimal doping. In the heavily doped regime, we find both strong electron-hole asymmetry and a persistent presence of Mott spectral features. Finally, we discuss the applicability of the single-band Hubbard model to describe the evolution of nodal spectra measured by angle-resolved photoemission spectroscopy (ARPES) on the single-layer cuprate La 2– x Sr x CuO 4 (0 ≤ x ≤ 0.15). This work benchmarks the predictive power of the Hubbard model for electronic properties of high- T c cuprates.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

The optimal co-doping of SrFe 1-x Co x O 3-δ oxygen carriers in redox applications

Although the oxygen carrier SrCoO 3 has higher redox activity than SrFeO 3 , cobalt is both more expensive and scarcer than iron, which would hinder the wide implementation of SrCoO 3 . For these reasons, doping SrFeO 3 with Co is a potential compromise, benefitting the redox properties of SrFeO 3 , while still limiting the overall amount of cobalt being used. In this work, to find the optimal level of Co-doping, density functional theory calculations were performed to investigate the Co-doping effect on the oxygen vacancy formation and oxygen migration in SrFe 1- x Co x O 3- δ ( x = 0, 0.125, 0.25, 0.375, 0.5). Our findings show that the oxygen vacancy formation energies ( E f ) decrease with the increase of Co content resulting from the increased composition of the O-2p band at the Fermi level upon Co doping. In particular, the E f decreases nearly 0.5 eV between the x = 0 and x = 0.25 samples while E f only decreases 0.1 eV further as Co content is increased to x = 0.5. We obtain that x = 0.25 is an optimal cost/benefit ratio for Co doping, which is preserved at both low oxygen vacancy concentrations ( δ = 0.0625 values listed above) and at high concentrations of δ = 0.1875 and 0.375. Kinetically, the oxygen migration barrier has slight change upon Co doping due to the similar size of Co and Fe. Therefore, considering both redox activity and economics in reversible oxygen storage applications, x = 0.25 is suggested as the optimal Co-doping value in SrFe 1- x Co x O 3- δ .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Microscopic model of the doping dependence of linewidths in monolayer transition metal dichalcogenides

A fully microscopic model of the doping-dependent exciton and trion linewidths in the absorption spectra of monolayer transition metal dichalcogenides in the low temperature and low-doping regime is explored. The approach is based on perturbation theory and avoids the use of phenomenological parameters. In the low-doping regime, we find that the trion linewidth is relatively insensitive to doping levels, while the exciton linewidth increases monotonically with doping. On the other hand, we argue that the trion linewidth shows a somewhat stronger temperature dependence. The magnitudes of the linewidths are likely to be masked by phonon scattering for T ≥ 20 K in encapsulated samples in the low-doping regime. We discuss the breakdown of perturbation theory, which should occur at relatively low-doping levels and low temperatures. Our work also paves the way toward understanding a variety of related scattering processes, including impact ionization and Auger scattering in clean 2D samples

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Electronic structure and effective mass of pristine and Cl-doped CsPbBr 3

Organic–inorganic lead halide perovskites (LHPs) have attracted great interest owing to their outstanding optoelectronic properties. Typically, the underlying electronic structure would determinate the physical properties of materials. But as for now, limited studies have been done to reveal the underlying electronic structure of this material system, comparing to the huge amount of investigations on the material synthesis. The effective mass of the valance band is one of the most important physical parameters which plays a dominant role in charge transport and photovoltaic phenomena. In pristine CsPbBr 3 , the Fröhlich polarons associated with the Pb–Br stretching modes are proposed to be responsible for the effective mass renormalization. In this regard, it would be very interesting to explore the electronic structure in doped LHPs. Here, we report high-resolution angle-resolved photoemission spectroscopy (ARPES) studies on both pristine and Cl-doped CsPbBr 3 . The experimental band dispersions are extracted from ARPES spectra along both $\overline{\Gamma}$–$\overline{M}$–$\overline{\Gamma}$ and $\overline{X}$–$\overline{M}$–$\overline{X}$ high symmetry directions. DFT calculations are performed and directly compared with the ARPES data. Our results have revealed the band structure of Cl-doped CsPbBr 3 for the first time, which have also unveiled the effective mass renormalization in the Cl-doped CsPbBr 3 compound. Doping dependent measurements indicate that the chlorine doping could moderately tune the renormalization strength. These results will help understand the physical properties of LHPs as a function of doping.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Electron Tunneling and X-Ray Photoelectron Spectroscopy Studies of the Superconducting Properties of Nitrogen-Doped Niobium Resonator Cavities

Scanning tunneling microscopy and spectroscopy and X-ray photoelectron spectroscopy (XPS) have been used to investigate the differences between the surface electronic structures and chemical structure of typically prepared and N-doped Nb cutouts from superconducting radio frequency (SRF) cavities. The goal of this work is to get insights into the fundamental physics and materials mechanisms behind the striking decrease of the surface resistance with the radiofrequency magnetic field, which has been observed by many groups on N-doped Nb cavities. In particular, we address the effects of N-doping on the superconducting properties at the surface of SRF cavities. XPS measurements reveal a significantly more oxidized Nb 3d states on the N-doped Nb surfaces which is confirmed by tunneling spectroscopy measurements. Analysis of the tunneling spectra in the framework of a recent model (A. Gurevich and T. Kubo Phys. Rev. B 96, 184515 (2017)) shows that the N-doping greatly reduces local distribution of superconducting properties on the surface, causes a significant shrinkage of the metallic suboxide and changes the contact resistance between the metallic suboxide and the bulk niobium toward an optimum value, resulting in a lower surface resistance. Combination of these factors enables one to effectively tune the density of states at the surface and to reveal the decrease of the surface resistance with the radio frequency field which follows from the BCS theory. A slightly reduced average gap and a smaller coherence length, revealed by tunneling spectroscopy in the vortex cores, have been found in the N-doped Nb samples compared to typically prepared Nb samples, indicating a stronger impurity scattering caused by nitrogen doping in a moderately disordered material.

Lechner, Eric M.↗
DOE OSTI2021

Orbital and spin character of doped carriers in infinite-layer nickelates

The recent discovery of superconductivity in Nd1-xSrxNiO2 has drawn significant attention in the field. A key open question regards the evolution of the electronic structure with respect to hole doping. Here we exploit x-ray absorption spectroscopy (XAS) and resonant inelastic x-ray scattering (RIXS) to probe the doping-dependent electronic structure of Nd1-xSrxNiO2. Upon doping, a high-energy feature in Ni L3-edge XAS develops in addition to the main absorption peak, while XAS at the O K-, Nd M3- and Nd M5-edge exhibits a much weaker response. This implies that doped holes are mainly introduced into Ni 3d states. By comparing our data to atomic multiplet calculations including D4h crystal field, the doping-induced feature in Ni L3-edge XAS is consistent with a d8 spin-singlet state in which doped holes reside in the 3dx2-y2 orbitals. This is further supported by the softening of RIXS orbital excitations due to doping, corroborating with the Fermi level shift associated with increasing holes in the Ni 3dx2-y2 orbital.

2-dimensional systems↗
DOE OSTI2023

Electronic structure, magnetic properties, spin orientation, and doping effect in Mn 3 Si 2 Te 6

The layered material Mn 3 Si 2 Te 6 , with alternating stacking honeycomb and triangular layers, is attracting considerable attention due to its rich physical properties. Here, in this study, using density functional theory and classical Monte Carlo (MC) methods, we systematically study this system with the 3d 5 electronic configuration. Near the Fermi level, the states are mainly contributed by Te 5p orbitals hybridized with Mn 3d orbitals, resembling a charge-transfer system. Furthermore, the spin orientations of the ferrimagnetic (FiM) ground state display different conductive behaviors when along the ab plane or out-of-plane directions: insulating vs metallic states. The energy difference between the FiM [110] insulating and FiM [001] metallic phases is very small (~0.71 meV/Mn) . Changing the angle θ of spin orientation from in-plane to out-of-plane directions, the band gaps of this system are gradually reduced, leading to an insulator-metal transition, resulting in an enhanced electrical conductivity, related to the colossal angular magnetoresistance (MR) effect. Although the three main magnetic couplings were found to be antiferromagnetic, overall the ground state is FiM. In addition, we also constructed the magnetic phase diagram using the classical XY spin model studied with the MC method. Three magnetic phases were obtained, including antiferromagnetic order, noncollinear spin patterns, and FiM order. Moreover, we also investigated the Se and Ge doping into the Mn 3 Si 2 Te 6 system: the FiM state has the lowest energy among the magnetic candidates for both Se- and Ge-doped cases. The magnetic anisotropy energy (MAE) decreases in the Se-doped case because the Mn orbital moment is reduced as the doping x increases. Due to the small spin-orbit-coupling effect of Se, the insulator-metal transition caused by the spin orientation disappears in the Se-doped case, resulting in an insulating phase in the FiM [001] phase. This causes a reduced colossal angular MR. However, both the MAE and the band gap of the Ge-doped case do not change much with increasing doping x . Our results for Mn 3 Si 2 Te 6 could provide guidance to experimentalists and theorists working on this system or related materials.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Effect of Doping Density on the Performance of Metamorphic GaInAs Solar Cells Grown by Dynamic Hydride Vapor Phase Epitaxy

We study the effect of doping density on the performance of inverted metamorphic ~1 eV GaInAs solar cells grown by dynamic hydride vapor phase epitaxy. We find that the doping efficiency of Se in this material is extremely high, with 5x10 17 cm -3 being the lowest controlled value we could achieve with our present Se source. We compared rear heterojunction devices grown with intentional n-doping of 5x10 17 cm -3 and unintentional n-doping of 5x10 15 cm -3 . The intentionally doped sample exhibited an open circuit voltage ~80 mV higher than the unintentionally doped sample due to reduced dark current, and a bandgap voltage offset, or W OC , of 0.407 V. We believe that future doping optimization will improve carrier collection and W OC in these devices.

GaAs↗
DOE OSTI2023

Synthesis and optical properties of phosphorus doped ZnO: X-ray absorption, X-ray emission, and X-ray excited optical luminescence studies

Abstract Over the past decades, zinc oxide semiconductor and its derivatives have been extensively developed because of its optoelectronic properties. Since ZnO is an intrinsic n-type semiconductor, how to synthesize high-quality p-type ZnO semiconductors and investigate their optoelectronic properties and local chemical structures are important and necessary. In this article, two studies of synthesizing both undoped and phosphorus-doped ZnO nanostructures by hydrothermal method and chemical vapor deposition (CVD) technique are presented. Scanning electron microscopy (SEM) and laboratory X-ray diffraction (XRD) are used to track the surface morphology and the crystalline structure of both undoped and phosphorus doped ZnO nanostructures, respectively. X-ray absorption near edge structures (XANES), X-ray emission spectroscopy (XES) and X-ray excited optical luminescence (XEOL) are also used to determine the local chemical information of both undoped and phosphorus-doped ZnO nano/microstructures such as local symmetry and optical properties. It is found that the phosphorus is successfully doped into the surface of ZnO and substituted the Zn. The phosphorus-doped ZnO products have better crystallinity and less oxygen vacancies on the surface. These two are correlated as one leads to the other. The XEOL results suggest that the average bandgap for undoped and phosphorus doped ZnO is the same, 3.24 eV. The second derivative of the absorption-emission spectra yields the fundamental bandgap for undoped ZnO and phosphorus-doped ZnO is 3.25 eV. The implication of this observation is discussed.

Chemistry↗
DOE OSTI2022

A New Low-Temperature Approach for Efficient and Low-Cost Group V Doping in CdTe Thin Film Solar Cells (Final Technical Report)

The goal of this project is to develop a highly efficient low-temperature ex-situ Group V diffusion doping approach in the CdCl 2 treated polycrystalline CdTe film using the group V chlorides (i.e., PCl 3 , AsCl 3 , SbCl 3 , and BiCl 3 ) as dopants source. For the first time, our innovative doping strategies through the low-temperature ex-situ Group V doping process in polycrystalline CdSeTe successfully demonstrated a promising power conversion efficiency of ~19% compared to the Cu-doped counterparts. Our newly developed low-temperature ex-situ group V doping allows dedicated control of group V diffusion amount, generates a desirable depth profile, and is completely compatible with commercial CdTe module manufacturing. We built the partnership with the largest CdTe solar module manufacturing in the US, e.g., First Solar, Inc to further develop these low-temperature diffusion doped CdSeTe solar cells. Our technology was granted US Patent No. US11257977B2. In this project, we systematically investigate and characterize the new ex-situ group V doping mechanisms, defect chemistry, microstructure, and device physics in CdTe solar cells by combining experimental and theoretical means to pave the way to achieve lower cost toward $\$$0.02/kWh and higher power conversion efficiency (PCE) toward 25% in polycrystalline CdTe solar technology. This project will benefit the public by providing more affordable solar electricity and provide an effective way to address climate change.

14 SOLAR ENERGY↗
NASA NTRS1989

Multiple doping of silicon-germanium alloys for thermoelectric applications

It is shown that heavy doping of n-type Si/Ge alloys with phosphorus and arsenic (V-V doping interaction) by diffusion leads to a significant enhancement of their carrier concentration and possible improvement of the thermoelectric figure of merit. High carrier concentrations were achieved by arsenic doping alone, but for a same doping level higher carrier mobilities and lower resistivities are obtained through phosphorus doping. By combining the two dopants with the proper diffusion treatments, it was possible to optimize the different properties, obtaining high carrier concentration, good carrier mobility and low electrical resistivity. Similar experiments, using the III-V doping interaction, were conducted on boron-doped p-type samples and showed the possibility of overcompensating the samples by diffusing arsenic, in order to get n-type behavior.

Fleurial, Jean-Pierre↗
NASA NTRS2024

Morphology and Luminescence Properties of Transition Metal Doped Zinc Selenide Crystals

Zinc selenide is an excellent matrix material to dope with rare-earth and transition metal to achieve mid-infrared luminescence to develop high power lasers. The luminescence, morphology and refractive index is significantly affected by the doping and defects generated due to size and valency of dopants, concentration, growth process and convection during the growth. The aim of the study is to investigate effect of point and line defects generated due to low doping of iron and chromium on the emission and morphology of the zinc selenide. Luminescence and morphological properties of large iron and chromium doped zinc selenide single crystals were studied to evaluate the effect of extremely low residual impurities and defects associated with the doping process. The emission properties following both short wavelength (i.e., ultraviolet; 350 – 370 nm) excitation and longer wavelength (i.e., near infrared; 850 – 870 nm) excitation were characterized. Luminescence emission bands were identified in both doped crystals. In addition to the primary emission bands, satellite peaks and intra-center transitions were also observed. Due to local population defects associated with the residual impurities (ppm to ppb) in the Fe-ZnSe and Cr-ZnSe crystals, peak emission wavelengths were observed to shift. Raman studies using 266 and 532 – nm excitation revealed different positions of longitudinal and transverse peaks for Fe-ZnSe and Cr-ZnSe crystals, associated with different levels of defects due to the different ion sizes. The emission bands were found to decrease in intensity due to recombination of residual impurity co-dopants and complex defects generated during growth and fabrication. Cryogenic temperature analyses revealed a very clean emission band due to freezing of some of the point and line defects. An emission band observed at 980 nm for both crystals at room temperature as well as cryogenic temperatures indicates a vibronic peak in ZnSe. The scanning electron microscopy (SEM) images of the local morphology support the conclusion that small crystallites in doped crystals are also present.

Zinc selenide↗