Effect Of Post-growth Annealing Research Articles

Post-growth annealing effect of Li-doped NiO thin films grown by mist chemical vapor deposition

Nickel oxide (NiO) thin films were grown by mist chemical vapor deposition (mist CVD) with various amounts of Li dopant in the precursor (0–15 %). As the Li dopant readily decomposed under the high temperature above 700℃, the post-growth annealing was conducted at 600–800 °C. The crystal quality of the undoped and Li-doped NiO films was improved by thermal annealing due to the crystal reconstruction. The optical transmittance of NiO films was decreased with increasing the amounts of Li dopants, whereas it was increased with thermal annealing. The bandgap of the NiO films was slightly red-shifted with increased amounts of Li dopants, whereas it was blue-shifted with increasing annealing temperature. The resistivity of as-grown NiO films ranged from 25–75 Ω·cm with Li doping. Electrical properties abruptly decreased under a high annealing temperature of 700 °C. Hence, an appropriate combination of Li doping and post-growth annealing might improve the structural properties of the NiO thin films while retaining the p-type conductivity.

Effects of high-temperature annealing on vacancy complexes and luminescence properties in multilayer periodic structures with elastically strained GeSiSn layers

Effects of postgrowth high-temperature annealing on vacancy complexes and photoluminescence (PL) from GeSiSn/Si multiple quantum wells (MQWs) are studied. The series of PL peaks related to the vacancy-tin complexes was observed for as-grown samples including different structures, such as GeSiSn/Si MQWs, multilayer periodic structure with GeSiSn quantum dots (QDs), GeSn cross-structures upon GeSiSn/Si MQWs, and thick GeSiSn layers. The PL band intensity is significantly reduced after annealing at 700 °C corresponding to the reduction in vacancy density, as demonstrated by the positron annihilation spectroscopy (PAS) data. Such annealing also results in the appearance of the PL signal related to the interband optical transitions in GeSiSn/Si MQWs. However, the high temperature could negatively impact the sharpness of heterointerfaces due to Sn diffusion, thus limiting the PL efficiency. To improve the luminescence properties of GeSiSn/Si structures, we proposed a two-stage technique combining both the annealing and subsequent treatment of samples in a hydrogen plasma at 200 °C. The plasma treatment significantly reduces the PL band of vacancy-related defects, whereas annealing at a moderate temperature of ∼600 °C prevents the blurring of heterointerfaces. As a result, we demonstrate an increase in the relative efficiency of interband PL of type II GeSiSn/Si MQW structures emitting in the range of 1.5–2 μm.

Effect of isothermal annealing on the optical properties of Ca<sub>3</sub>TaGa<sub>3</sub>Si<sub>2</sub>O<sub>14</sub> crystals

The effect of post-growth isothermal annealing in vacuum and in air on the optical properties of Ca3TaGa3Si2O14 crystal samples of Z and X-cuts has been studied. Spectral dependences of transmission coefficients were measured in the wavelength range (240–700) nm taking into account anisotropy and dichroism. On the Z-cut samples in the initial state an absorption band at λ = 360 nm in the ultraviolet range is observed, in the visible region – two absorption bands at λ = 460 nm and λ = 605 nm. Additionally, a band at λ = 290 nm was observed on the X-cut samples. When the sample was rotated around the direction of the light beam by 90 degrees, a change in the intensity of the absorption bands was observed. Annealing in vacuum leads to a decrease in the intensity of the absorption bands in the near ultraviolet and visible range, except for the absorption band at λ = 605 nm. Annealing in air leads to the opposite effect – an increase in the intensity of the absorption bands, except for the band λ = 605 nm. The value of the anomalous birefringence of the samples was estimated by the Mallard method. The degree of linear dichroism is calculated. It is shown that the degree of dichroism decreases as a result of annealing in vacuum, and increases during annealing in air.

Effect of postgrowth annealing in an oxygen-containing atmosphere on the microhardness of single-crystal calcium molybdate CaMoO4

Effect of postgrowth annealing in an oxygen-containing atmosphere on the microhardness of single-crystal calcium molybdate CaMoO4

The effect of annealing treatment on the structural and optical properties of nanostructured CuxO films obtained by 3D printing

This work studies the effect of post-growth annealing on the structural and optical properties of copper oxide films. Thin films were obtained by 3D printing on glass substrates using ink based on a suspension of CuO nanoparticles. To optimize their structural characteristics and optical quality, the samples were subjected to thermal annealing for 30 min in an argon environment at different temperatures from 250 °C to 500 °C. The obtained samples were studied by scanning electron microscopy, X-ray diffraction, energy dispersive X-Ray, Raman, optical and photoelectric spectroscopy. Based on the obtained results, the main structural and substructural characteristics of the films were established, such as lattice parameters, unit cell volume, texture, sizes of coherent scattering regions, and the level of microdeformation, as well as their dependence on the annealing temperature. In addition, the nature of optical absorption, band gap energies for various types of electronic transitions, and the optical quality of the studied nanostructured copper oxide films were determined. It was shown that CuO films annealed at 350 °C have the best crystalline and optical quality. It was established that at an annealing temperature above 400 °C, a phase transition from the tenorite phase to the cuprite phase is observed. At the same time, a change in the films' substructural characteristics is already observed at Ta = 400 °C. Optimal thermal annealing conditions of CuxO films for effective control of their phase composition have been established.

Post-growth enhancement of CVD-grown hexagonal boron nitride films on sapphire

This study explores the effect of post-growth annealing on hexagonal boron nitride (hBN) films grown on c-sapphire substrates by chemical vapor deposition as post-growth annealing proves to overcome the equipment limitations of commercial thermal CVD systems and offers a simplistic way to enhance the properties of the as-grown hBN films useful for multiple-wafer scalability, thereby making it a practical approach for industrial manufacturing of high-quality hBN films. hBN films are grown at 1100 °C by CVD process and are annealed up to 1300 °C under nitrogen atmosphere in an annealing furnace system. It is observed that the annealed hBN films are continuous and have a pronounced granular structure as compared to the as-grown hBN films. The annealed BN films retain the 1:1 B:N stoichiometry and the hexagonal phase as observed in the as-grown hBN films. The optical bandgap of the annealed hBN films is augmented from 5.70 eV to 5.82 eV as a result of the annealing treatment, indicating enhanced optical properties.

Ferroelectricity in dopant-free HfO2 thin films prepared by pulsed laser deposition

As a high-k material, hafnium oxide (HfO2) has been used in gate dielectrics for decades. Since the discovery of polar phase in Si-doped HfO2 films, chemical doping has been widely demonstrated as an effective approach to stabilize the ferroelectric phase in HfO2 based thin films. However, the extra capping layer deposition, post-growth annealing and wake-up effect are usually required to arouse the ferroelectricity in HfO2 based thin films, resulting in the increase of complexity for sample synthesis and the impediment of device application. In this study, the ferroelectricity is observed in non-capped dopant-free HfO2 thin films prepared by pulsed laser deposition (PLD) without post-growth annealing. By adjusting the deposited temperature, oxygen pressure and thickness, the maximum polarization up to 14.7 μC/cm2 was obtained in 7.4 nm-thick film. The fraction of orthorhombic phase, concentrations of defects and size effects are considered as possible mechanisms for the influences of ferroelectric properties. This study indicates that PLD is an effective technique to fabricate high-quality ferroelectric HfO2 thin films in the absence of chemical doping, capping layer deposition and post-growth annealing, which may boost the process of nonvolatile memory device application.

Effects of Growth Ambient, Process Pressure, and Heat Treatments on the Properties of RF Magnetron Sputtered GaMgZnO UV-Range Transparent Conductive Films

Effects of growth variables and post-growth annealing on the optical, structural and electrical properties of magnetron-sputtered Ga0.04Mg0.10Zn0.86O films are characterized in detail. It is observed that films grown from pure oxygen plasma showed high resistivity, ~102 Ω·cm, whereas films grown in Ar plasma showed much lower resistivity, 2.0 × 10− 2 ~ 1.0 × 10−1 Ω·cm. Post-growth annealing significantly improved the electrical resistivity, to 4.3 ~ 9.0 × 10−3 Ω·cm for the vacuum annealed samples and to 1.3 ~ 3.0 × 10−3 Ω·cm for the films annealed in Zn vapor. It is proposed that these phenomena may be attributed to the improved crystalline quality and to changes in the defect chemistry. It is suggested that growth within oxygen environments leads to suppression of oxygen vacancy (Vo) donors and formation of Zn vacancy (VZn) acceptors, resulting in highly resistive films. After annealing treatment, the activation of Ga donors is enhanced, Vo donors are annihilated, and crystalline quality is improved, increasing the electron mobility and the concentration. After annealing in Zn vapor, Zn interstitial donors are introduced, further increasing the electron concentration.

1 eV GaAsSbN–based solar cells for efficient multi-junction design: Enhanced solar cell performance upon annealing

In this work, we demonstrate the beneficial effect of post-growth rapid thermal annealing (RTA) on the performance of ~1 eV GaAsSbN-based solar cells. Different configurations of the dilute nitride material are studied: a bulk quaternary GaAsSbN layer and type-II GaAsSb/GaAsN superlattices (SL) with different period thickness. The RTA treatment leads in both types of structures to an enhanced external quantum efficiency (EQE) and reduced values of the dark saturation current and series resistance. The origin of these improvements is attributed to reduced densities of N and Sb-rich clusters and point defects. Remarkably, all solar cell parameters are substantially improved, this being particularly significant for the short circuit current density (JSC) and power conversion efficiency (PCE), the latter with a relative enhancement as high as 500%. The large increment of JSC is an important step towards current–matching in multi–junction solar cells containing GaAsSbN structures.

Judging phase purity of hematite (α-Fe2O3) nanoparticles through structural and magnetic studies

The effect of post-growth annealing on the phase transformation leading to phase pure hematite (α-Fe2O3) nanoparticles is reported in this work. Co-precipitation technique was used to synthesise iron oxide nanoparticles by adjusting the pH of the solution. The xerogel was dried at 80 °C and the obtained powder was calcined in the temperature range 400–800 °C for 3 h. in air. Annealing temperature was prefixed on the basis of the thermal degradation pattern of the starting precursor. X-ray diffraction (XRD) study endorsed the presence of mixed phases FeO, FeO2 and α-Fe2O3 in the as-prepared sample. On annealing, the minor phases transform gradually to α-Fe2O3, as confirmed through thermal studies. Performed Rietveld analysis confirms the presence of impurity phases in samples annealed at low temperature. Phase pure sample crystallizes in the rhombohedral corundum structure (space group, R-3c) with a = 5.04044 Å, c = 13.7628 Å and c/a = 2.73048. FT-Raman spectral investigations allowed for a clear assignment of the α-Fe2O3 phase. Chemical analysis advocated the only presence of Fe3+ ions that octahedrally coordinated with hexagonally close packed O2- ions that constitute corundum structure. Electron microscopy (TEM) images proved the non-spherical particle distribution in the range 80–100 nm with mean particle size of 93 nm. Structural phase transition with annealing temperature was further confirmed through the fluctuations in the magnetic structure. In analogues to XRD, magnetic study also served as a judging tool to identify purity and the presence of mixed phases in hematite.

Post-growth annealing effects on charge and spin excitations in Nd2−xCexCuO4

We report a Cu K- and L$_3$-edge resonant inelastic x-ray scattering study of charge and spin excitations of bulk Nd$_{2-x}$Ce$_x$CuO$_4$, with focus on post-growth annealing effects. For the parent compound Nd$_2$CuO$_4$ ($x = 0$), a clear charge-transfer gap is observed in the as-grown state, whereas the charge excitation spectra indicate that electrons are doped in the annealed state. This is consistent with the observation that annealed thin-film and polycrystalline samples of RE$_2$CuO$_4$ (RE = rare earth) can become metallic and superconducting at sufficiently high electron concentrations without Ce doping. For $x = 0.16$, a Ce concentration for which it is known that oxygen reduction destroys long-range antiferromagnetic order and induces superconductivity, we find that the high-energy spin excitations of non-superconducting as-grown and superconducting annealed crystals are nearly identical. This finding is in stark contrast to the significant changes in the low-energy spin excitations previously observed via neutron scattering.

Thermal Annealing Effects on Naturally Contacted Monolayer MoS2

Transition metal dichalcogenides such as MoS2, which can be produced in monolayer form, have attracted attention because of their interesting and potentially useful electrical and optical properties. These properties often depend sensitively on material properties such as defect density and crystallinity. Herein, the effects of postgrowth annealing on monolayer MoS2 grown using a novel chemical vapor deposition process are investigated. In this process bulk molybdenum patterns serve as the nucleation site and source material for high‐quality MoS2 material growth. After postgrowth thermal annealing, the photoluminescence is found to blueshift and become more uniform up to an annealing temperature of 300 °C. At higher temperatures, isolated monolayers begin to crack along the grain boundaries, which leads to variations in luminescence, whereas after annealing temperature of 200 °C, material anchored to the molybdenum patterns is found to easily ablate.

Synthesis and Memristor Effect of a Forming-Free ZnO Nanocrystalline Films.

We experimentally investigated the effect of post-growth annealing on the morphological, structural, and electrophysical parameters of nanocrystalline ZnO films fabricated by pulsed laser deposition. The influence of post-growth annealing modes on the electroforming voltage and the resistive switching effect in ZnO nanocrystalline films is investigated. We demonstrated that nanocrystalline zinc oxide films, fabricated at certain regimes, show the electroforming-free resistive switching. It was shown, that the forming-free nanocrystalline ZnO film demonstrated a resistive switching effect and switched at a voltage 1.9 ± 0.2 V from 62.42 ± 6.47 (RHRS) to 0.83 ± 0.06 kΩ (RLRS). The influence of ZnO surface morphology on the resistive switching effect is experimentally investigated. It was shown, that the ZnO nanocrystalline film exhibits a stable resistive switching effect, which is weakly dependent on its nanoscale structure. The influence of technological parameters on the resistive switching effect in a forming-free ZnO nanocrystalline film is investigated. The results can be used for fabrication of new-generation micro- and nanoelectronics elements, including random resistive memory (ReRAM) elements for neuromorphic structures based on forming-free ZnO nanocrystalline films.

Effect of thermal oxidation on the optical, electrical, and chemical properties of zinc nitride films grown by reactive magnetron sputtering

We have studied the effect of post growth annealing in oxygen ambient on the optical, chemical and electronic properties of zinc nitride thin films. The films were prepared by reactive radio frequency magnetron sputtering of zinc target in the presence of argon and nitrogen gasses at a substrate temperature of 300 °C. Post growth annealing was performed at annealing temperatures of 300, 400, 500, 600, and 700 °C in the oxygen environment to transform the zinc nitride films into p-type zinc oxide. Atomic force microscopy of the films reveal that surface roughness and grain size of the films are directly proportional to the post-growth annealing temperature. X-ray photoelectron spectroscopy of the films revealed that as-grown film has the highest intensity of nitrogen in the film whereas little nitrogen remains in the films that were annealed at 500 °C and higher temperatures. Films annealed at higher temperatures have lower carrier concentration but higher Hall mobility compared to the as-grown film and the films annealed at lower temperature. Moreover, as-grown film and the films annealed at lower temperature have n-type conductivity whereas films annealed at temperatures above 500 °C exhibit p-type conductivity. Films annealed at lower temperature have bandgap values closer to the zinc oxynitride but bandgap of the films annealed at higher temperatures have values close to the bandgap of zinc oxide. This indicates that post growth annealing of zinc nitride films at 500 °C in oxygen ambient transforms it into p-type zinc oxide.

Influence of oxygen-rich and zinc-rich conditions on donor and acceptor states and conductivity mechanism of ZnO films grown by ALD—Experimental studies

Understanding the origin of the strong difference of electrical parameters between as grown and annealed undoped ZnO films prepared at a temperature range of 100–200 °C by thermal atomic layer deposition is essential for their future applications. In this paper, we show that the conductivity drop by up to 4 orders of magnitude as effect of post-growth annealing is accompanied by multiple simultaneous effects like a two orders of magnitude decrease of hydrogen impurity content, a strong width reduction of the luminescence peaks, and an increase of crystallite sizes influencing the carrier scattering. We show that a level of structural and optical improvement as well as the final electrical parameters of annealed films strongly depend on the previously employed growth temperature, which is related to transition from oxygen- to zinc-rich conditions influencing a type and concentration of native point defects. The growth temperature does not only influence the bandgap energy but also the binding energies of existing donors and the relative ratio between the number of donors and acceptors; hence, it determines the final electrical characteristics of the films. This means that electrical properties of undoped ZnO-atomic layer deposition films can be tuned by native defects engineering.

The effect of post-growth rapid thermal annealing on InAs/InGaAs dot-in-a-well structure monolithically grown on Si

The effect of post-growth annealing (PGA) on dot-in-well (DWELL) structures grown on Si substrates has been studied. The photoluminescence (PL) measurements showed that, compared to the DWELL structures directly grown on GaAs, the PGA process induces a distinct difference in the tuning of the emission properties. Then, transmission electron microscopy imaging of the samples revealed that PGA improved the uniformity of quantum dots (QDs) while the size of the QDs increased, in agreement with a corresponding red shift and a decrease of the full width at half maximum in the PL emission spectrum. Finally, energy-dispersive x-ray linescan provided a quantitative analysis of the composition change of DWELL grown on Si in the as-grown, 700 °C annealed, and 800 °C annealed samples. The change in the InL/GaK concentration ratio became gradual between the QDs and surrounding materials after 800 °C annealing. The analysis of the optical properties, morphology evolution, and compositional change of the QDs as a function of the annealing temperature showed good agreement.

Effect of thermal annealing on the strain and microstructures of in-situ phosphorus-doped [formula omitted] films grown on blanket and patterned silicon wafers

In this study, in-situ phosphorus-doped Si1−xCx layers were epitaxially grown on blanket and patterned Si wafers using reduced pressure chemical vapor deposition (RPCVD). The effect of post-growth annealing on the strain and microstructures of the epilayers was investigated by high resolution X-ray diffraction (HR-XRD), Raman scattering, and high resolution transmission electron microscopy (HR-TEM) analyses. Structural investigation revealed that induced tensile strain became significantly less at temperatures over 900°, as confirmed by Raman scattering measurements of SiC vibration modes. Furthermore, strain relaxation and substantial Csub loss were found in XRD and Raman data of Si:C samples annealed at 1000°, resulting from the generation of defects such as β-SiC precipitates or dislocations in Si1−xCx epilayers. Moreover, our microstructural analyses using TEM showed the formation of the β-SiC precipitates during rapid thermal annealing (RTA) over 900° and an increase in their number and size with annealing temperatures up to 1000°. Finally, we examined the impact of thermal annealing on the local strain and microstructures of patterned Si1−xCx samples with different structures. Our findings will provide greater insight into evaluating the strain states and microstructure of as-grown and annealed P-doped Si1−xCx films on both blanket and patterned Si wafers.

Accurate band alignment at the amorphous Al2O3 /p-Ge(100) interface determined by hard x-ray photoelectron spectroscopy and density functional theory

We have investigated the band alignment at the interface of amorphous aluminum oxide (am-${\mathrm{Al}}_{2}{\mathrm{O}}_{3}$) grown by atomic layer deposition on p-Ge(100) and the effects of postgrowth annealing using hard x-ray photoelectron spectroscopy and density function theory (DFT). Accurate determination of the valence-band offsets was obtained by comparing the experimentally measured valence bands with DFT-calculated densities of states. The am-${\mathrm{Al}}_{2}{\mathrm{O}}_{3}$ density of states calculated from a weighted ensemble of crystalline ${\mathrm{Al}}_{2}{\mathrm{O}}_{3}$ structures gives excellent agreement with experiment, sufficiently capturing the nonlinear shape of the valence-band edge. We report a valence-band offset of $2.60\ifmmode\pm\else\textpm\fi{}0.1$ eV for am-${\mathrm{Al}}_{2}{\mathrm{O}}_{3}$/p-Ge, which is reduced by 0.20 eV upon annealing as interfacial ${\mathrm{GeO}}_{x}$ is formed.

Post-growth annealing effect on the performance of Cu2SnSe3 solar cells

In this work, the effect of post-deposition annealing in selenium environment was studied on Cu2SnSe3 thin film solar cells prepared from solid solution by doctor blade method. XRD pattern confirms deposited films are of polycrystalline nature having cubic phases with (1 1 1) orientation. The crystallinity improves with the increase in annealing temperature. At high annealing temperature surface agglomeration was found which is due to the melting and re-evaporation of the components from the surface. Electrical properties like carrier mobility, conductivity also modified with the increase in annealing temperature. Maximum efficiency of 1.17% was achieved for the sample annealed at 400 °C having barrier height (ϕb), ideality factor (n) and series resistance (Rs) nearly equal to 0.71 eV, 1.5 and 69 Ω respectively.

Eu-Doped AlGaN/GaN Superlattice-Based Diode Structure for Red Lighting: Excitation Mechanisms and Active Sites

In this work, we have established the effects of postgrowth annealing and Eu implantation, followed by annealing on an AlGaN/GaN superlattice-based diode structure, containing Mg-doped GaN top p-cap layers. The study is based on the combined information from different optical techniques, such as Raman, photoluminescence, and photoluminescence excitation. We have shown that the diode structure exhibits a stable crystalline quality even after annealing under high temperature and high pressure (HTHP) conditions (1400 °C in 1 GPa N2). Furthermore, we have demonstrated that the implanted Eu ions reached the first quantum wells of the diode structure and that the postimplantation thermal annealing partly removed the implantation defects, recovering some of the as-grown luminescence and optically activating the Eu3+ in the diode structure. An in-depth study of the Eu3+ population mechanisms was realized through room temperature photoluminescence excitation. A model was built based on the different excitation bands originated from the materials present in the diode structure, demonstrating that an energy transfer between the AlGaN/GaN superlattice excitons and the Eu3+ ions occurs, therefore enlarging the excitation pathways for the ion’s red luminescence. In addition, Eu3+ luminescence was observed not only with above but also with below GaN bandgap excitation. The temperature dependent study of the 5DJ → 7FJ transitions allowed to tentatively provide the Eu3+ intraionic assignments of the diode structure. We have demonstrated that at least three nonequivalent active sites are created by the Eu implantation in the diode structure: Eu1, Eu2, and Eu–Mg defect in both configurations Eu0 and Eu1(Mg).