Rapid Thermal Annealing Research Articles

Ohmic contacts to n-type SiC: Influence of Au and Ta intermediate layers

In this study, the optimization of metal-semiconductor contacts to reduce the contact resistance of ohmic contacts on n-type 4H-SiC. The commonly used Ni/Au metal scheme served as a reference. We introduced two novel metal schemes: (i) incorporating a thin interfacial Au layer (2 nm) into Ni/Au, resulting in Au/Ni/Au, and (ii) introducing a thin intermediate barrier layer of Ta (20 nm) into Ni/Au, resulting in Ni/Ta/Au. Rapid thermal annealing (RTA) is performed at different temperatures and durations and the electrical characteristics of the contacts are measured. X-ray diffraction analysis was employed to investigate the intermediate phases formed during annealing. In the Au/Ni/Au metal scheme, the presence of Au at the interface promoted the formation of additional phases of nickel-silicide (Ni3Si and Ni3Si2). Compared to the traditional Ni/Au scheme, the modified metal schemes led to lower surface roughness and reduced contact resistance. Specific contact resistivity values are calculated, 2.2 × 10−5 Ω-cm2 for Ni/Au, 1.37 × 10−5 Ω-cm2 for Au/Ni/Au, and 4.84 × 10−5 Ω-cm2 for Ni/Ta/Au. This research offers valuable insights for the selection of metal schemes in designing ohmic contacts on n-type SiC, with potential applications in various semiconductor device technologies.

Phosphorus doped Li2FeSiO4 thin films prepared by magnetron sputtering as high-performance thin-film cathode materials

Polycrystalline Li2FeSiO4 (LFS) and Li2FePxSi1-xO4 (LFSP) thin film cathode materials tested in quasi-solid thin-film Li-ion cells have been synthesized using radio frequency magnetron sputtering in combination with rapid thermal annealing. The thin films were characterized for their phase and morphology using X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The charge transport properties and electrochemical performance of the films were evaluated through constant current charge-discharge tests, cyclic voltammetry, rate performance testing, electrochemical impedance spectroscopy (EIS), and galvanostatic intermittent titration technique (GITT). The research findings revealed that after the sputtering growth process, during rapid annealing at 850 °C, the as prepared amorphous Li2FeSiO4 thin film showed selective crystalline growth, while crystallized grains on the surface of Li2FeSi0.95P0.05O4 thin films exhibited a fusion like and relatively regular distribution. The electronic conductivity and ionic conductivity of Li2FeSi0.95P0.05O4 thin films were measured at 6.60 × 10−7 S·cm−1 and 4.87 × 10−7 S·cm−1, respectively. The Li2FeSi0.95P0.05O4 thin film displayed an initial discharge specific capacity of 224.05 mAh g−1 at a rate of 0.1 C, with a capacity retention of 73.5 % after 100 cycles in half-cell structure. The assembled Li2FeSi0.95P0.05O4/Li1.3Al0.3Ti1.7(PO4)3/Li quasi-solid-state battery presented an initial discharge specific capacity of 195.62 mAh g−1 at 0.1 C, with a capacity retention of 55.03 % after 100 cycles. This study offers a valuable reference for the fabrication and doping modification of poly-anion-type Li2FeSiO4 cathode thin film materials, thus aiding the progress of next-generation thin-film quasi-solid-state lithium-ion batteries.

Photoluminescence of dense arrays of InGaPAs/InGaAs quantum dots formed by substitution of group V elements

One drawback of self-organized quantum dots is their low optical gain. The development of new shaping methods that would allow higher gain, for example, due to a higher surface density of the QD array, remains an important task to date. In the present work, arrays of quantum dots have been formed by substituting phosphorous atoms with arsenic ones in a thin InGaP epilayer. Based on transmission electron microscopy data, the surface density was estimated to be about 1.3 × 1012 cm−2, which is one of the highest values for quantum dots on GaAs. The influence of an additional InGaAs epilayer (quantum well) on the luminescence properties of quantum dots was investigated in a wide temperature range and different optical pumping levels. It was found that placing the quantum well under the layer of quantum dots has little effect on the central emission wavelength, while quantum dots covered with the InGaAs demonstrate a strong red shift of the luminescence spectrum. A transition from a nonequilibrium to an equilibrium distribution of charge carriers over quantum-dot states, related to the lateral transport of charge carriers over quantum dot array, similar to that previously observed in In(Ga)As Stranski-Krastanow quantum dots, was revealed. This is manifested in a change in temperature dependencies of the linewidth and peak position of the photoluminescence band. For the structures under study, this transition occurs at a temperature of about 125 K. Rapid thermal annealing of the structures allows to increase the integrated photoluminescence intensity of quantum dots up to 4 times, while the maximum of the spectrum remains almost unchanged, provided that the annealing temperature does not exceed 620 °C.

Acoustically driven ferromagnetic resonance in YIG thin films

Acoustically driven ferromagnetic resonance (ADFMR) is a platform that enables efficient generation and detection of spin waves via magnetoelastic coupling with surface acoustic waves (SAWs). While previous studies successfully achieved ADFMR in ferromagnetic metals, there are only few reports on ADFMR in magnetic insulators such as yttrium iron garnet (Y3Fe5O12, YIG) despite more favorable spin wave properties, including low damping and long coherence length. The growth of high-quality YIG films for ADFMR devices is a major challenge due to poor lattice-matching and thermal degradation of the piezoelectric substrates during film crystallization. In this work, we demonstrate ADFMR of YIG thin films on LiNbO3 (LNO) substrates. We employed a SiOx buffer layer and rapid thermal annealing for crystallization of YIG films with minimal thermal degradation of LNO substrates. Optimized ADFMR device designs and time-gating measurements were used to enhance the ADFMR signal and overcome the intrinsically low magnetoelastic coupling of YIG. YIG films have a polycrystalline structure with an in-plane easy direction due to biaxial stresses induced during cooling after crystallization. The YIG device shows clear ADFMR patterns with maximum absorption for H ≈ 160 mT parallel to SAW propagation, which is consistent with our simulation results based on existing theoretical models. These results expand possibilities for developing efficient spin wave devices with magnetic insulators.

Energy-Dispersive X-Ray Microanalysis – as a Method for Study the Aluminium-Polysilicon Interface after Exposure with Long-Term and Rapid Thermal Annealing

Energy dispersive X-ray microanalysis is one of the main methods for determining the elemental composition of matter. Possessing high locality and a relatively shallow penetration depth of the electron beam (< 1 μm), this method has found wide application in the field of microelectronics, as the main method for analyzing the elemental composition of matter. The method allows to study the surface of a substance both pointwise and over an area with the construction of element distribution maps. In the paper we investigated the influence of long-term and rapid heat treatments on the formation of the aluminum-polysilicon interface in order to study the formation of ohmic contacts in the element base of integrated circuits. The aluminumpolysilicon interface was studied using energy-dispersive X-ray microanalysis. It has been established that during long-term thermal annealing (450 °C, 20 min) polysilicon is completely dissolved in aluminum followed by its segregation in the form of separate agglomerates in the aluminum film, which can lead to a complete failure of the integrated circuit. During rapid thermal annealing (450 °C, 7 s) such a phenomenon was not detected. Thus it is advisable to use rapid thermal annealing as an alternative to traditional long-term thermal annealing in microelectronics. This makes it possible to significantly reduce the dissolution of polysilicon in aluminum, avoid the destruction of ohmic contacts and increase the percentage of yield of workable 0products in the process of integrated circuits' manufacturing.

The Influence of Annealing on the Compositional and Crystallographic Properties of Sputtered Li–Al–O Thin Films

Li–Al–O materials are interesting for several applications. Herein, a Li–Al–O thin‐film materials library, deposited by inert magnetron sputtering and postdeposition annealing in O2 atmosphere, is used to study the effects of different annealing temperatures (300–850 °C) and durations (1 min to 7 h) on crystallinity and composition of the films. X‐ray photoelectron spectroscopy depth profiling reveals inhomogeneous compositional depth profiles of conventionally annealed films (300–650 °C, 3–7 h) with increased Li contents toward the film surface and increased Al contents toward the film–substrate interface, as confirmed by a combination of Rutherford backscattering spectrometry and deuteron‐induced nuclear reaction analysis. The minimum temperature for the formation of crystalline LiAlO2 in the otherwise amorphous films is 550 °C. The undesired inhomogeneous depth profiles are transformed into homogeneous ones by rapid thermal annealing (750–850 °C, 1–10 min), while simultaneously causing the formation of crystalline LiAlO2. Therefore, rapid thermal annealing is shown to be more suitable than conventional annealing for the thermal processing of Li–Al–O thin films. Moreover, this conclusion is expected to have broader relevance beyond Li–Al–O materials, as it is likely to apply to other Li metal oxides, of which there are many technologically relevant ones.

Impact of post-ion implantation annealing on Se-hyperdoped Ge

Hyperdoped germanium (Ge) has demonstrated increased sub-bandgap absorption, offering potential applications in the short-wavelength-infrared spectrum (1.0–3.0 μm). This study employs ion implantation to introduce a high concentration of selenium (Se) into Ge and investigates the effects of post-implantation annealing techniques on the recovery of implantation damage and alterations in optical properties. We identify optimal conditions for two distinct annealing techniques: rapid thermal annealing (RTA) at a temperature of 650 °C and ultrafast laser heating (ULH) at a fluence of 6 mJ/cm2. The optimized ULH process outperforms the RTA method in preserving high doping profiles and achieving a fourfold increase in sub-bandgap absorption. However, RTA leads to regrowth of single crystalline Ge, while ULH most likely leads to polycrystalline Ge. The study offers valuable insights into the hyperdoping processes in Ge for the development of advanced optoelectronic devices.

Effect of temperature on the stability and performance of III-nitride HEMT magnetic field sensors

The study aimed to investigate the underlying physics limiting the temperature stability and performance of non-surface passivated Al0.34Ga0.66N/GaN Hall effect sensors, including contacts, under atmospheric conditions. The results obtained from analyzing the microstructural evolution in the Al0.34Ga0.66N/GaN Hall sensor heterostructure were found to correlate with the electrical performance of the Hall effect sensor. High-resolution x-ray photoelectron spectroscopy studies revealed the signature of surface oxidation in the GaN cap layer, as well as a slight out-diffusion of “Al” from the AlGaN barrier layer. To prevent the formation of a bumpy surface morphology at the Ohmic contact, we investigated the impact of “Pt” top Ohmic contacts. The application of a top “Pt” contact stack resulted in a smooth Ohmic contact surface and provided evidence that the bumpy surface morphology in Au-based Ohmic contacts is due to the formation of an Al-Au viscous alloy during rapid thermal annealing. In the early stages of thermal aging, the small drop in contact resistivity stabilized with subsequent thermal aging past the initial 550 h at 200 °C. The outcome is that the Al0.34Ga0.66N/GaN Hall effect sensors, even without surface passivation, exhibited a stable response to applied magnetic fields with no sign of significant degradation after 2800 h of thermal aging at 200 °C under atmospheric conditions. This observed stability in the Hall sensor without surface passivation can be attributed to a self-imposed surface oxidation of the cap layer during the early stages of aging, which serves as a protective layer for the device during subsequent extended periods of thermal aging at 200 °C.

Effects of Rapid Heat Treatments on the Properties of Cu2O Thin Films Deposited at Room Temperature Using an Ammonia-Free SILAR Technique

We report herein the analysis of the properties of copper(I) oxide thin films deposited by an optimized ammonium-free successive ion layer adsorption and reaction (SILAR) technique. The Cu2O thin film deposition process was carried out at room temperature using copper acetate monohydrate, sodium citrate as complexing agent, and hydrogen peroxide as precursors of copper and oxygen ions, respectively. The harmless and easy-to-handle sodium citrate replaces the volatile NH4OH commonly employed as complexing agent in the SILAR technique for the deposition of metal oxide thin films. The optical, structural, morphological, and electrical properties of the as-deposited Cu2O thin films were studied as a function of the number of cycles during deposition, as well as their modifications produced by the effect of rapid thermal annealing (RTA) in vacuum in a temperature range of 200–250°C for 1 min, 3 min, and 5 min. The as-deposited thin films had cubic crystalline structure corresponding to the Cu2O phase as determined by x-ray diffraction (XRD), with a direct energy bandgap of 2.43–2.51 eV depending on the number of cycles, and electrical resistivity of the order of 103 Ω cm. The XRD and x-ray photoelectron spectroscopy (XPS) analysis of the Cu2O thin films treated by RTA demonstrated an increase of the crystal size with time and temperature of the RTA and reduction effects from Cu2+ to Cu1+ oxidation states. On the other hand, the RTA treatments also decreased their energy bandgap to 2.38 eV and electrical resistivity to 102 Ω cm. The high energy bandgap values of the Cu2O thin films were attributed to quantum confinement effects produced by their small crystal size in the range of 3.6–8.6 nm.Graphical

The synergistic effect of Ta-doping and antireflective TaOx layer on the thermochromic VO2 thin films for smart windows

Current efforts to promote the use of VO2 materials as a promising candidate for thermochromic smart windows continue to be hindered by the low luminous transmittance (Tlum), the limited solar modulation ability (ΔTsol), the high phase transition temperature (Tt, ∼68 °C) and the wide thermal hysteresis (ΔT). The present work addresses these issues by fabricating an antireflective TaOx layer on the Ta-doped VO2 (i.e., VO2(Ta)) thin films. The VO2(4.35 at% Ta) thin films with low Tt of 29.87 °C and narrowed ΔT of almost zero were grown on glass substrates by magnetron sputtering at room temperature followed by rapid thermal annealing. However, the VO2(Ta) thin films show slightly enhanced Tlum of 38.31 % compared with undoped VO2 films (35.46 %) and decreased the ΔTsol by 1.83 %. The thermochromic properties are further enhanced by depositing the antireflective TaOx layer onto the VO2(Ta) thin film by reactive magnetron sputtering, which significantly increases the Tlum from 38.31 % to 48.58 %, marginally decreases the ΔTsol from 4.44 % to 4.12 %, and maintain the Tt and ΔT constant. These results verify the possibility of developing VO2 films with simultaneously increased optical transmittance, decreased Tt to suitable values, and extremely narrow ΔT by using the synergistic effect of element doping and constructing an antireflective layer.

Effect of repeating hydrothermal growth processes and rapid thermal annealing on CuO thin film properties.

This paper presents an investigation into the influence of repeating cycles of hydrothermal growth processes and rapid thermal annealing (HT+RTA) on the properties of CuO thin films. An innovative hydrothermal method ensures homogeneous single-phase films initially. However, their electrical instability and susceptibility to cracking under the influence of temperature have posed a challenge to their utilization in electronic devices. To address this limitation, the HT+RTA procedure has been developed, which effectively eliminated the issue. Comprehensive surface analysis confirmed the procedure's ability to yield continuous films in which the content of organic compounds responsible for the formation of cracks significantly decreases. Structural analysis underscored the achieved improvements in the crystalline quality of the films. The implementation of the HT+RTA procedure significantly enhances the potential of CuO films for electronic applications. Key findings from Kelvin probe force microscopy analysis demonstrate the possibility of modulating the work function of the material. In addition, scanning capacitance microscopy measurements provided information on the changes in the local carrier concentration with each repetition. These studies indicate the increased usefulness of CuO thin films obtained from the HT+RTA procedure, which expands the possibilities of their applications in electronic devices.

P-Type ZnO Films Made by Atomic Layer Deposition and Ion Implantation.

Zinc oxide (ZnO) is a wide bandgap semiconductor that holds significant potential for various applications. However, most of the native point defects in ZnO like Zn interstitials typically cause an n-type conductivity. Consequently, achieving p-type doping in ZnO is challenging but crucial for comprehensive applications in the field of optoelectronics. In this work, we investigated the electrical and optical properties of ex situ doped p-type ZnO films. The p-type conductivity has been realized by ion implantation of group V elements followed by rapid thermal annealing (RTA) for 60 s or flash lamp annealing (FLA) on the millisecond time scale in nitrogen or oxygen ambience. The phosphorus (P)-doped ZnO films exhibit stable p-type doping with a hole concentration in the range of 1014 to 1018 cm-3, while antimony (Sb) implantation produces only n-type layers independently of the annealing procedure. Microstructural studies of Sb-doped ZnO show the formation of metallic clusters after ms range annealing and SbZn-oxides after RTA.

Metal oxides for electronics and the SPQEO journal

This article discusses the main trends in the physics and preparation of metal oxides and summarizes the results of research published by SPQEO in this area over the past decade. The main metal oxides studied include ZnO, Zn1-xCdxO, Zn1-xCoxO, MgxZn1–xO, ZnO:Mn, VO2, ZrO2–Y2O3, TiO2, WO3, Gd2O3, Er2O3, WO3–CaO–SiO2–B2O3: Tb3+, Dy2O3, NiO, FexOy, Ga2O3, Al2O3, ITO, Ag2O and graphene oxide. These oxides were obtained by the following methods: sintering in air or in a stream of various gases, magnetron sputtering, atomic layer deposition, explosive evaporation, sol-gel, spin coating, spray pyrolysis, rapid thermal annealing, green synthesis from plant solutions, melt quenching, rapid thermal annealing, self-ignition, ion-plasma co-sputtering, vacuum sputtering, reactive ion beam sputtering, and the Hammer method. The electrical and optical properties of the studied oxides are illustrated.

Investigation of Ge/Sn/Al2O3 multilayer structure for photodetector application

Photodetectors with considerably high performance working in a wide wavelength range extending from UV to IR are essential for technological applications. The present work primarily focuses on the multilayer structure of Ge/Sn/Al2O3 deposited on Si substrate for visible to short wave infrared (SWIR) broadband photodetector applications. The synthesis of a multilayered structure was carried out using electron beam evaporation. Subsequently, these samples were subjected to rapid thermal annealing (RTA). The crystalline nature of films after RTA was examined using X-ray diffraction, and Raman spectroscopy. Afterward, the photodetector measurements were carried out on the fabricated device. The device structure shows better responsivity, external quantum efficiency, detectivity, and noise equivalent power with varying optical power and voltage. The measured responsivity, external quantum efficiency, and detectivity are 1.07 A/W, 125 %, and 2.1 × 109 Jones, respectively. The results indicated the possibility of using the Ge/Sn/Al2O3 multilayered structure as visible to SWIR photodetector.

Ferroelectric properties and current mechanisms of BaTiO3/Nb:SrTiO3 thin films

[Formula: see text] thin film oxides have been deposited on [Formula: see text] substrates using a pulsed laser deposition system. Different annealing methods were thereafter used to assess the ferroelectricity of the grown films. The residual polarization value, 2Pr, of 4.205 [Formula: see text]C/cm2 and saturated residual polarization value, 2Pmax, of 15.484 [Formula: see text]C/cm2 were obtained using in-situ annealing. After performing rapid thermal annealing (RTA) annealing, the residual polarization value rose to 4.676 [Formula: see text]C/cm2 and the saturated residual polarization value rose to 18.723 [Formula: see text]C/cm2. Furthermore, a comparison of results showed that the saturation test frequency of the in-situ annealing was 10 times higher than the saturation test frequency of the RTA. This could be explained by the fact that the secondary high-temperature annealing led to a decrease in the conductivity of the doped oxide and, thereby, a decrease in the effective electric field that was applied to both ends of the BTO ([Formula: see text]) film. Thus, a lower frequency was required to ensure a flip of all ferroelectric domains within the BTO film. By testing the fatigue frequency at 100 kHz, [Formula: see text] stable cycles in both annealing methods and the results confirmed the good stability of the device performance. A linear fit analysis of the [Formula: see text] – [Formula: see text] curves showed under in-situ annealing the presence of both a bulk-limited current mechanism that was dominated by the space charge limited current (SCLC) and Pool–Frenkel (PF) mechanisms, and an interface-limited current that was dominated by the Fowler–Nordheim (FN) mechanism in the structure. After RTA annealing, the conducting mechanism is ohmic contact at low electric field and the SCLC mechanism at high field strength. The results show that after RTA annealing, the quality and ferroelectric properties of the films are significantly improved compared to those under in-situ annealing. These results showed that the BTO/NSTO/STO ([Formula: see text]) structure had a standard test frequency as well as reliable stability. The BTO/NSTO/STO structure showed, therefore, promising applications in future nonvolatile information memory devices.

Effect of rapid thermal annealing on DC performance of Mg0.30Zn0.70O/Cd0.15Zn0.85O MOSHFET

This study focuses on a cost-effective method for fabrication of a metal oxide semiconductor-heterostructure field effect transistor (MOSHFET) based on MgZnO/CdZnO (MCO) using dual ion beam sputtering (DIBS), in contrast to the more expensive epitaxial growth system. The MOSHFETs developed in this research exhibit notable characteristics, such as a substantial two-dimensional electron gas (2DEG) transconductance (∼2.6 mS), a high ION/IOFF response ratio in the order of 108, and minimal gate leakage current. Furthermore, we explore the impact of rapid thermal annealing (RTA) on the drain current at various temperatures (600 °C and 800 °C). The results indicate a fourfold improvement in drain current compared to unannealed conditions, primarily attributed to reduced contact resistance and no degradation in term of MgZnO/CdZnO structure. Additionally, an analysis of post-RTA treatment under a nitrogen (N2) atmosphere on gate leakage current is presented. The investigation spans temperatures ranging from 400 °C to 800 °C, revealing that above 600 °C (gate leakage at 400 °C–600 °C is around ∼10−9 A), gate leakage in HFET is augmented by one order of magnitude (∼10−8 A) due to a phase change in the dielectric. These findings underscore the feasibility of DIBS-grown MCO MOSHFETs as an economical solution for the mass production of switching devices and sensors.

Design, development, and performance of a versatile graphene epitaxy system for the growth of epitaxial graphene on SiC.

A versatile graphene epitaxy (GrapE) furnace has been designed and fabricated for the growth of epitaxial graphene (EG) on silicon carbide (SiC) in diverse growth environments ranging from high vacuum to atmospheric argon pressure. Radio-frequency induction enables heating capabilities up to 2000 °C, with controlled heating ramp rates achievable up to 200 °C/s. The details of critical design aspects and temperature characteristics of the GrapE system are discussed. The GrapE system, being automated, has enabled the growth of high-quality EG monolayers and turbostratic EG on SiC using diverse methodologies, such as confinement-controlled sublimation (CCS), open configuration, polymer-assisted CCS, and rapid thermal annealing. This showcases the versatility of the GrapE system in EG growth. Comprehensive characterizations involving atomic force microscopy, Raman spectroscopy, and low-energy electron diffraction techniques were employed to validate the quality of the produced EG.

Highly transparent and conductive Ga-doped InWO multi-component electrodes for Perovskite photovoltaics

Wide-bandgap Ga-doped InWO (GIWO) transparent conductive electrodes (TCE) were fabricated by co-sputtering IWO and Ga2O3, followed by rapid thermal annealing (RTA), with the effects of the Ga dopant content on the electrical, optical, structural, and morphological properties of the GIWO multi-component electrodes investigated to optimize the GIWO electrode. According to the figure of merit (FOM), the GIWO film with a Ga content of 2.1 at% exhibited a low sheet resistance of 9.9 Ohm/square and high transmittance of 91.71 % at a wavelength of 550 nm. The presence of a high Lewis acid strength (LAS) dopant of Ga (1.16) and W (3.15) led to an increase in the carrier mobility of GIWO and transmittance in the near infrared wavelength region. In addition, the strongly preferred (222) and (400) orientations of the GIWO grains increase the carrier mobility and improve the surface morphology of the GIWO electrodes. The successful operation and superior performance of the planar p-i-n structured perovskite solar cells (PSC) fabricated on GIWO electrodes indicate the feasibility of GIWO as a substitute for conventional Sn-doped In2O3 electrodes. The highest-performing PSC with GIWO electrodes exhibited reliable hysteresis with an efficiency difference of less than 1 % depending on the scan direction under standard AM1.5 G conditions.

Heteroepitaxially grown homojunction gallium oxide PN diodes using ion implantation technologies

Although advancements in n- and p-doping of gallium oxide (Ga2O3) are underway, the realization of functional pn diodes remains elusive. Here, we present the successful fabrication of a Ga2O3 pn diode utilizing ion implantation technology. The Ga2O3 epilayers were grown on c-plane sapphire substrates by metalorganic chemical vapor deposition (MOCVD). P-type conductivity Ga2O3 epilayer, confirmed by Hall effect analysis, was achieved by phosphorus (P) ion implantation followed with a rapid thermal annealing (RTA) process. This p-Ga2O3 epilayer reveals a significant reduction in resistivity (<106) compared to undoped Ga2O3, demonstrating the successful inclusion and activation of P within the crystal lattice. X-ray diffraction analysis shows that the Ga2O3 epilayers were grown in high crystal quality. Although the crystallinity of Ga2O3 was slightly degraded after P ion implantation, the structure was recovered to high-quality crystal after RTA treatment. For the device structure, p-type Ga2O3 was formed first, followed n-type Ga2O3 regrowth to create a pn junction diode. The obtained results demonstrate a built-in voltage of 4.8 V, 4.2 V, and 4.308 V from simulation, fabricated pn diodes measured by I–V and C–V, respectively. A high breakdown voltage of 900 V was also obtained for the lateral pn diode grown on sapphire substrate. As concerning temperature stability, I–V curves of Ga2O3 pn diode were measured from 25oC to 150oC in steps of 25 °C. At elevated temperatures, for both forward and reverse biases, consecutive increasing currents were measured. These could be resulted from dominant diffusion and drift currents over recombination current at a given bias. In addition, the reverse current saturated (@V > 3kT/q) and remained very low at 2✕10−8 A, as the diode operated at 150oC. The behavior could be due to Ga2O3 being a wide bandgap material.

Atomic level mechanism of disorder-order transformation kinetics at nanoscale in FePt based systems

L10 ordered FePt is one of the most promising materials for spintronic and recording media applications. In the present work, the mechanism of L10 phase transformation in FePt based films with varying initial structures is examined at the nanoscale to understand the ordering process using synchrotron based GIXRD, MOKE, VSM, and techniques with sub nanometer depth selectivity like XRR and SIMS. Precisely controlled compositions of the films are deposited using magnetron sputtering. Rapid thermal annealing is used for post-deposition processing. It is evaluated experimentally that for a shorter annealing time of 70 s at 400 °C, besides volume diffusion, short circuit diffusion paths along the intercrystallite region owing to the presence of nanostructured grains play a dominant role in alloying behavior. A study of the L10 ordering process reveals the crucial role of film structure in controlling the transformation kinetics, texturing of nanograins, and magnetic coercivity. Diffusion studies disclose that type B diffusion kinetics is activated for the annealing time during which L10 transformation occurs in the films.