Argon Annealing Research Articles

Improvement of N-type carbon nanotube field effect transistor performance using the combination of yttrium diffusion layer in HfO2 dielectrics and metal contacts.

In this paper, we obtained n-type top-gate carbon nanotube thin film field effect transistors (CNTFET) with source/drain extensions structure through dielectrics optimization strategy, combining the yttrium layer with HfO2 dielectric argon annealing process and metal contacts. The mechanism for enhanced n-type conduction was explained as being due to the vertical diffusion of yttrium to the HfO2 dielectric during argon annealing. This diffusion causes abending of the energy band, which results in more positive fixed charges and a reduction in the electron injection barrier between the low work function source-drain Cr electrode and carbon nanotube. The optimized technology has great prospects for the low cost, large scale and high performance n-type CNTFET to be used in integrated electronic devices.&#xD.

Enhancing UV photoresponse in zinc oxide derived from zeolitic imidazolate framework-8 through argon annealing: a study on charge trap mitigation and photocurrent dynamics

Enhancing UV photoresponse in zinc oxide derived from zeolitic imidazolate framework-8 through argon annealing: a study on charge trap mitigation and photocurrent dynamics

Novel cable‐like tin@carbon whiskers derived from the Ti2SnC MAX phase for ultra‐wideband electromagnetic wave absorption

AbstractOne‐dimensional (1D) metals are well known for their exceptional conductivity and their ease of formation of interconnected networks that facilitate electron migration, making them promising candidates for electromagnetic (EM) attenuation. However, the impedance mismatch from high conductivity and their singular mode of energy loss hinder effective EM wave dissipation. Construction of cable structures not only optimizes impedance matching but also introduces a multitude of heterojunctions, increasing attenuation modes and potentially enhancing EM wave absorption (EMA) performance. Herein, we showcase the scalable synthesis of tin (Sn) whiskers from a Ti2SnC MAX phase precursor, followed by creation of a 1D tin@carbon (Sn@C) cable structure through polymerization of PDA on their surface and annealing in argon. The EMA capabilities of Sn@C significantly surpass those of uncoated Sn whiskers, with an effective absorption bandwidth reaching 7.4 GHz. Remarkably, its maximum radar cross section reduction value of 27.85 dB m2 indicates its exceptional stealth capabilities. The enhanced EMA performance is first attributed to optimized impedance matching, and furthermore, the Sn@C cable structures have rich SnO2/C and Sn/SnO2 heterointerfaces and the associated defects, which increase interfacial and defect‐induced polarization losses, as visually demonstrated by off‐axis electron holography. The development of the Sn@C cable structure represents a notable advancement in broadening the scope of materials with potential applications in stealth technology, and this study also contributes to the understanding of how heterojunctions can improve EMA performance.

Phase formation, structure and properties of quaternary MAX phase thin films in the Cr-V-C-Al system: A combinatorial study

Tailoring of individual atomic layers via alloying to synthesize quaternary MAX phases allows for expanding their chemical diversity and fine-tuning of their properties. In this study, Cr-V/C/Al multilayered precursors were deposited via combinatorial magnetron sputtering, creating nanostructured architectures with periodic stacking of nanolayers and varying Cr:V ratios. Their phase transformation and underlying reaction mechanisms during subsequent thermal annealing in argon towards the prospective quaternary solid solution (CrV)n+1AlCn MAX phases formation was systematically studied. Crystallization of (CrV)2AlC starts at approximately 500°C, while growth of higher-ordered (CrV)4AlC3 is observed from 960°C. Notably, intergrowth of (CrV)2AlC and (CrV)4AlC3 structures with coherent interface suggests that (CrV)2AlC acts as template for nucleation of (CrV)4AlC3. Thermal stability and high-temperature oxidation tests found that (CrV)2AlC exhibits higher thermal stability compared to (CrV)4AlC3 and films with Cr72.7V27.3 displayed good oxidation resistance at 1000°C, forming a protective bilayer oxide scale consisting of (Cr,Al)2O3 and Al2O3.

The influence of deposition conditions on the surface morphology and luminescent properties of (Y0.06Ga0.94)2O3:Cr thin films

Thin films of (Y0.06Ga0.94)2O3:Cr were obtained by radio-frequency (RF) ion-plasma sputtering in an argon atmosphere on polycrystalline polycor and amorphous υ-SiO2 substrates. The surface morphology of the films was studied by atomic force microscopy. It was found that during argon annealing of (Y0.06Ga0.94)2O3:Cr thin films on υ-SiO2 substrates, grain growth occurs perpendicular to the substrate surface. The results of studies of the photoluminescence and cathodoluminescence luminescence of the investigated films are presented. It is shown that thin films of (Y0.06Ga0.94)2O3:Cr on υ-SiO2 substrates under photoexcitation emit in the blue region of the spectrum and this luminescence is due to the luminescence of the (Y0.06Ga0.94)2O3 matrix. Under cathodic excitation, the activator luminescence of the Cr3+ ion dominates with a maximum in the region around 700 nm, due to the electronic transitions 4T2 → 4A2.

Surface modification and coherence in lithium niobate SAW resonators

Lithium niobate is a promising material for developing quantum acoustic technologies due to its strong piezoelectric effect and availability in the form of crystalline thin films of high quality. However, at radio frequencies and cryogenic temperatures, these resonators are limited by the presence of decoherence and dephasing due to two-level systems. To mitigate these losses and increase device performance, a more detailed picture of the microscopic nature of these loss channels is needed. In this study, we fabricate several lithium niobate acoustic wave resonators and apply different processing steps that modify their surfaces. These treatments include argon ion sputtering, annealing, and acid cleans. We characterize the effects of these treatments using three surface-sensitive measurements: cryogenic microwave spectroscopy measuring density and coupling of TLS to mechanics, X-ray photoelectron spectroscopy and atomic force microscopy. We learn from these studies that, surprisingly, increases of TLS density may accompany apparent improvements in the surface quality as probed by the latter two approaches. Our work outlines the importance that surfaces and fabrication techniques play in altering acoustic resonator coherence, and suggests gaps in our understanding as well as approaches to address them.

Surface morphology change in DLC: H coatings with gradient Cr under high temperature and high pressure

The pressure influence of the surface morphology of DLC: H Coatings with gradient Cr (DCr) was studied by annealing in argon (HT effect) and HIPping (HT/HP effect). The results show that the voids formed on the HIPping annealed surface are rose-shaped with multi-layered edges but the edge of the voids formed on the argon annealed surface looks single-layered, and the composition of the coating surface is the same after HIPping and argon annealing. The Cr content at the bottom of the voids is higher in the HIPped surface than the argon annealed surface, and the voids formed in the HIPping annealed are relatively smaller but deeper than those in the argon. It is reasonable to deduce that the hydrogen release could have been restricted by the applied high compressive pressure on the surface.

Calibrated in-vacuum quantum efficiency system for metallic and III-V thin-film photocathodes

The construction and calibration of a high vacuum system for thin film growth and in situ quantum efficiency (QE) measurement are described. Surface cleaning by in situ argon ion sputtering and annealing is supported. The QE measurement is based on an external 265 nm LED and in situ positively biased collector grid. The system is applied to two metallic and two semiconducting photocathodes: polycrystalline silver and copper, and single crystal InP and InSb. Surface cleaning protocols are shown to have a dramatic effect on the QE for all of these materials. The maximum QE values achieved for clean InSb and InP are around 8 × 10−5, for Cu 9 × 10−5 and for Ag 2 × 10−4.

Construction of Fe0.64Ni0.36@graphite nanoparticles via corrosion-like transformation from NiFe2O4 and surface graphitization in flexible carbon nanofibers to achieve strong wideband microwave absorption

Recently, microwave absorption (MA) materials have attracted intensive research attention for their ability to counteract the effects of ever-growing electromagnetic pollution. However, conventional microwave absorbers suffer from complex fabrication processes, poor stability and different optimal thicknesses for minimum reflection loss (RLmin) and widest effective absorption bandwidth (EAB). To address these issues, we have used electrospinning followed by high-temperature annealing in argon to develop a flexible microwave absorber with strong wideband absorption. The MA properties of the carbon nanofibers (CNFs) can be tuned by adjusting annealing temperature, and are dependent on the composition and microstructure of the CNFs. The absorber membrane obtained at 800 °C consists of Fe0.64Ni0.36@graphite core–shell nanoparticles (NPs) embedded in CNFs, formed via a corrosion-like transformation from NiFe2O4 to Fe0.64Ni0.36 followed by surface graphitization. This nanostructure greatly enhances magnetic-dielectric synergistic loss to achieve superior MA properties, with an RLmin of −57.7 dB and an EAB of 6.48 GHz (11.20–17.68 GHz) both acquired at a thickness of 2.1 mm. This work provides useful insights into structure–property relationship of the CNFs, sheds light on the formation mechanism of Fe0.64Ni0.36@graphite NPs, and offers a simple synthesis route to fabricate light-weight and flexible microwave absorbers.

The effect of RTP pretreatment on slip-lines of argon annealed silicon wafer

In this research, Rapid Thermal Process (RTP) pretreatment technology was used to study the slip-lines of 12-inch light boron-doped silicon wafer with Oxidation Induced Stacking Fault (OISF) ring which will be used for argon annealing. X-ray Diffraction Topography (XRT) test results were shown that Rapid Thermal Processing (RTP) pretreatment below 1250 °C would lead to the deterioration of slip-lines during argon annealing, and that RTP pretreatment no less than 1250 °C would eliminate slip-lines. Bulk Micro Defects (BMD) tests show that RTP pretreatment can deteriorate or eliminate slip-lines resulted from argon annealing. When the RTP pretreatment temperature is lower than 1250 °C, the native BMD nuclei smaller than the critical size will eliminate. During argon annealing, the growth of the residual native BMD nuclei formed during ingot pulling process is the dominant process, while formation and growth of new nuclei are less, resulting in both the reduction of BMD density and broadening distribution of BMD size. Then we see the slip-lines of silicon wafer will become worse due to the increase of thermal stress in the silicon wafer. However, when the RTP pretreatment temperature is no less than 1250 °C, the native BMD nuclei will be completely eliminated and a vacancy enriched layer will be formed in the silicon wafer. During argon annealing, vacancies promote the uniform nucleation of BMD, the density of BMD increases and the size distribution becomes narrow, and the thermal stress in the silicon wafer is relatively lower, thus the slip-lines are eliminated.

Quasi-In Situ XPS Insights into the Surface Chemistry of Garnet-Type Li6.4La3Zr1.4Ta0.6O12 Solid-State Electrolytes: The Overlooked Impact of Pretreatments and a Direct Observation of the Formation of LiOH.

Garnet-type Li6.4La3Zr1.4Ta0.6O12 (LLZTO) is a highly promising solid-state lithium metal battery electrolyte due to its exceptional ionic conductivity and electrochemical stability. However, when exposed to air, a passivation layer can be spontaneously formed on the garnet-type electrolyte, deteriorating its wettability with metallic lithium (Li) and impeding the lithium ion transfer at the Li-garnet electrolyte interface. The passivation layer is considered a critical issue for garnet-type solid electrolytes. Despite intensive research, the formation mechanism of the passivation film remains poorly understood. The key to elucidating the formation mechanism is to obtain a pristine garnet electrolyte surface and study how the pristine garnet electrolyte interacts with air. In this study, different passivation layer removal pretreatments were performed to expose pristine garnet electrolytes, and their impacts on the samples were systematically studied. The results reveal the overlooked negative impacts of vacuum annealing and acid treatment on LLZTO, which are indicated by the severe loss of Li and O and the formation of additional Li-depleted metal oxides. It was confirmed that argon annealing is the only viable approach to remove the passivation layer without introducing concomitant contaminations to LLZTO. Based on this method, we directly evidenced the formation of LiOH on LLZTO under rarefied air using quasi-in situ X-ray photoelectron spectroscopy. It was confirmed that the loss of Li and O ions, rather than Li+/H+ exchange, drives the formation of LiOH in the passivation layer. These results not only provide a better understanding of the surface and interface chemistry of LLZTO but also reveal a reliable surface treatment for the LLZTO sample.

Effects of annealing environments on structural, surface topological and optical properties of Gd-doped ZnO films: a comparative study of argon and air annealing

Effects of annealing environments on structural, surface topological and optical properties of Gd-doped ZnO films: a comparative study of argon and air annealing

Synthesis of V2AlC thin films by thermal annealing of nanoscale elemental multilayered precursors: Incorporation of layered Ar bubbles and impact on microstructure formation

Periodically stacked nanoscale V/C/Al multilayered thin film precursors were deposited by magnetron sputtering using elemental targets. Their temperature-dependent phase transformation during subsequent thermal annealing in argon towards V2AlC MAX phase formation was investigated. Compositional and microstructural analyses at the nanoscale revealed undulation growth of the nanolayers and preferential incorporation of Ar atoms into amorphous carbon nanolayers within the as-deposited multilayered precursors. Single-phase and basal-plane-oriented V2AlC films were formed at annealing temperatures above 560 °C. The incorporated Ar atoms migrated and aggregated into high-density nanoscale Ar clusters/bubbles located essentially at grain boundaries after annealing, displaying pronounced layered distribution characteristics especially adjacent to the substrate/film interface. The heterogeneous incorporation of argon atoms or clusters in heterostructured films composed of multicomponent sublayers likely represents a common phenomenon during thin film nucleation and growth, while its impact on the macroscopic properties of films remains to be explored.

Microstructural evolution of pre-oxidized Cr-coated Zry-4 during annealing in argon

The annealing behavior of the pre-oxidized Cr-coated Zry-4 at 1200 °C in argon is systematically investigated. A Cr2O3 scale with a thickness of ∼9 μm formed on the sample surface after pre-oxidation of the Cr-coated Zry-4 in steam at 1200 °C for 30 min. During annealing in inert atmosphere, the thickness of the Cr2O3 scale decreases with the increase of the annealing time because of the reaction between the Cr2O3 scale and the outward diffused Zr at the Cr2O3/Cr interface, the decomposition of Cr2O3, and the inward diffusion of O into the Zircaloy substrate along the ZrO2 precipitates at the Cr grain boundaries. The Cr2O3 scale has completely transformed into Cr after annealing for one hour. Pores and Cr grains are observed inside the Cr2O3 scale after annealing due to the decomposition of Cr2O3. The ZrO2 precipitates at Cr grain boundaries gradually grow outward during the annealing and finally reach the outer surface of the Cr coating. The results in this paper provide new insights into the thickness decrease mechanism and the decomposition behavior of the Cr2O3 scale.

Enhancing the luminescence yield of Cr3+ in β -Ga2O3 by proton irradiation

In situ ion-beam-induced luminescence measurements reveal a strong enhancement of the Cr3+ emission yield in electrically conductive chromium doped β-Ga2O3 single crystals upon proton irradiation. The observed effect can be explained based on the Fermi-level pinning caused by radiation defects. This pinning of the Fermi level activates deep carrier traps that can act as sensitizers of the Cr3+ emission. In agreement with this model, in semi-insulating samples, where the Fermi level lies deep in the bandgap, the Cr3+ emission is present already in as-grown samples, and no enhancement of its intensity is observed upon proton irradiation. The boost of the Cr3+ emission yield by irradiation, observed in conductive samples, is reversed by thermal annealing in argon at temperatures above 550 °C for 30 s. The results reveal a high potential of Cr-doped β-Ga2O3 for in situ and ex situ optical radiation detection and dosimetry.

Effect of annealing atmosphere on the luminescence characteristics of CVD-ZnSe

The influence of the atmosphere of CVD-ZnSe annealing carried out in modes close to the procedure of their doping with iron on the luminescent characteristics of these crystals is investigated. It was found that annealing in the atmosphere of argon and selenium leads to a qualitative change in the impurity-defect composition and to a complex spatial distribution of the luminescent characteristics of CVD-ZnSe, especially in the crystal region at a distance of up to 400 microns from the surface. In the case of annealing in zinc, the luminescent characteristics are more uniform, with the exception of the near-surface zone with a width of about 100 microns, which has a high luminescence intensity in the entire spectral range under study (0.44-0.72 microns). The obtained results are interpreted on the basis of the assumption about the evaporation of zinc during annealing in argon and selenium. Based on the analysis of the spatial distribution of luminescence, assumptions are made about the nature of the observed impurity-defect centers. Keywords: two-photon confocal microscopy, CVD-ZnSe, impurity-defect composition, high temperature annealing.

High carrier mobility tungsten-doped indium oxide films prepared by reactive plasma deposition in pure argon and post annealing

Tungsten-doped indium oxide films were deposited by reactive plasma deposition using a low doped target in pure argon atmosphere at room temperature. Post thermal annealing was conducted in different atmospheres in the range of 150 °C–250 °C to improve the properties of films. The structural, electrical and optical properties of IWO films with different annealing conditions have been investigated. It is found that crystallization after annealing is an effective way to improve the mobility. The mobility of the polycrystalline films is much greater than amorphous films. And the ordered structure is conducive to interstitial oxygen and oxygen in the atmosphere to fill the oxygen vacancies, leading to the decrease of the carrier concentration and a further increase of the mobility. We have prepared IWO thin films with the carrier mobility (up to 83 cm2V−1s−1), even if as-deposited films had a relatively low carrier mobility (∼30 cm2V−1s−1). The optical transmittance of IWO films maintains 89% and 84% in visible and near-infrared regions, respectively. The mobility of IWO films is found to depend on the manufacture of the source target and the highest mobility of 120 cm2V−1s−1 has been reached.

Influence of annealing atmosphere on photoelectrochemical response of TiO2 nanotubes anodized under controlled hydrodynamic conditions

• Annealing in argon and nitrogen atmospheres increase oxygen vacancies formation. • Nitrogen atoms appear in the matrix of the crystalline TiO 2 annealed in nitrogen. • Band gap of nanostructures decreases annealing in non-oxidizing atmospheres. • Nitrogen or argon atmospheres increases the photocatalytic activity of nanotubes. The influence of three annealing atmospheres (air, nitrogen and argon) and the use of controlled hydrodynamic conditions (from 0 to 5000 rpm) on morphological, structural, chemical and photoelectrochemical properties of TiO 2 nanotubes have been evaluated. For this purpose, different characterization techniques have been used: Field Emission Scanning Electron Microscopy, Raman Confocal Laser Spectroscopy, X-Ray Diffraction, X-Ray Photoelectron Spectroscopy, Incident Photon-to-electron Conversion Efficiency measurements, ultraviolet–visible absorption spectra, Mott-Schottky analysis and photoelectrochemical water splitting tests. According to the results, it can be concluded that both hydrodynamic conditions and annealing in non-oxidizing atmospheres improve the photoelectrochemical response of the TiO 2 nanotubes. This fact has been attributed to the oxygen vacancies formed after annealing in argon and nitrogen atmospheres and also to the presence of nitrogen into the TiO 2 lattice due to the thermal treatment in the nitrogen atmosphere.

Spectroscopic studies of borohydride-derived cerium-doped zirconia nanoparticles under air and argon annealing conditions

Spectroscopic studies of borohydride-derived cerium-doped zirconia nanoparticles under air and argon annealing conditions

The role of FeCo and FeCoCr nanowires array on the formation of single phase bi-magnets

Nanowire (NWs) arrays of FeCo and FeCoCr were prepared by AC pulsed electrodeposition embedded into an alumina template. They were then employed as an underlayer to provide the dot array of cobalt ferrite thin films. Highly ordered arrays of NWs with the diameter of 30 nm and length of 10 µm were fabricated and then annealed in various environments. The cobalt ferrite thin films were deposited by the sputtering approach with the almost constant thickness of 70 nm as the hard magnetic phase. The combination of FeCo and cobalt ferrite could provide an exchange spring magnet with the magnetic coupling feature. X-ray diffraction (XRD) patterns of the NW arrays indicated the formation of the body centered cubic (bcc) FeCo phase with [110] texture. Field emission electron microscopy (FESM) equipped by EDS also characterized the morphological features and elemental composition. Magnetization and coercivity of NWs were examined using the vibrating sample magnetometer. The maximum coercivity of NWs array is 2950 Oe which is related to H2 annealing FeCo NWs array. The magnetization reversal process of the as-deposited and annealed FeCo and FeCoCr NWs arrays was performed by angular dependence coercivity and squareness. Further, FORC diagrams indicated an interacting single domain behavior for as-deposited FeCo NWs and a weakly-interacting single domain state for the annealed samples. The morphological and structural features of cobalt ferrite were also studied by XRD, FE-SEM and AFM techniques. It was found that the cobalt ferrite dot array with a uniform chemical composition and structure was formed. The inter-diffusion of atoms between underlayer and thin films was confirmed by EDS. The maximum coercivity of the nanocompsite was 5800 Oe that is obtained for FeCoCr underlayer with argon annealing. The VSM analysis showed that sufficient exchange coupling was formed by using the FeCoCr underlayer in hydrogen annealing, while argon annealing provided a kink in the hysteresis loops. The obtained nanocomposites could be, therefore, considered as the potential candidate for use in the exchange spring magnet.