High-pressure Annealing Research Articles

Pulse Switching Study on the HfZrO Ferroelectric Films With High Pressure Annealing

Hf0.5Zr0.5O2 (HfZrO) thin-film ferroelectric materials have recently drawn considerable attention due to their attractive properties such as large bandgap (>5 eV), extreme thin thickness ( ${\le} 10$ nm), and good Si-compatibility. However, high crystallization temperature (600 °C–1000 °C) and relatively low remanent polarization ( ${P}_{r}$ ) compared to conventional perovskite ferroelectric materials are not suitable for flexible energy related devices, and are insufficient to overcome the barriers of conventional ferroelectric memory. In this paper, we investigated the effect of high-pressure postmetallization annealing (HPPMA) on the ferroelectric properties of the HfZrO metal–ferroelectric–metal (MFM) devices. HfZrO MFM capacitors annealed at 450 °C/50 bar shows a ${P}_{r}$ value of over 20 $\mu \text{C}$ /cm2 which is very advanced ${P}_{r}$ value. Based on the short-pulse switching technique, we quantitatively and systematically examined the improved characteristics of HfZrO prepared by HPPMA in terms of coercive field ( ${E}_{c}$ ) and possibly involved interfacial capacitance ( ${C}_{i}$ ).

Optical properties of CVD single crystal diamonds before and after different post-growth treatments

Single crystal diamonds grown by chemical vapor deposition (CVD) before and after different post-growth treatments were studied using optical spectroscopy. The most pronounced changes in color were observed after irradiation with subsequent annealing at 800 °C whereas a weakening of gray tint took place after the high-pressure high-temperature annealing. Low-pressure high-temperature annealing in microwave plasmas of different composition and by electric arc discharge did not produce a noticeable effect on the diamond properties. Signals from nitrogen-vacancy complexes were detected in the absorption and luminescence spectra of CVD diamonds, but the pink tint in the irradiated and annealed diamonds is due to SiV complexes, not NV. The peaks at 150 and 262 K associated with boron were observed in thermoluminescence (TL) curve of original CVD diamonds. Combined irradiation and annealing allowed us to create deep traps of charge carriers responsible for TL peaks in the 430 to 470 K range, which made CVD diamonds promising for TL dosimetry.

Unique reliability characteristics of fully depleted silicon-on-insulator tunneling FET

This study investigated the unique reliability characteristics of tunneling field effect transistors (TFETs) by comparing the effects of positive bias temperature instability (PBTI) and hot carrier injection (HCI) stresses. In case of hot carrier injection (HCI) stress, the interface trap generation near a p/n+ region was the primary degradation mechanism. However, strong recovery after a high-pressure hydrogen annealing and weak degradation at low temperature indicates that the degradation mechanism of TFET under the HCI stress is different from the high-energy carrier stress induced permanent defect generation mechanism observed in MOSFETs. Further study is necessary to identify the exact location and defect species causing TFET degradation; however, a significant difference is evident between the dominant reliability mechanism of TFET and MOSFET.

High-pressure oxygen annealing of Al2O3 passivation layer for performance enhancement of graphene field-effect transistors

High-pressure annealing in oxygen ambient at low temperatures (∼300 °C) was effective in improving the performance of graphene field-effect transistors. The field-effect mobility was improved by 45% and 83% for holes and electrons, respectively. The improvement in the quality of Al2O3 and the reduction in oxygen-related charge generation at the Al2O3-graphene interface, are suggested as the reasons for this improvement. This process can be useful for the commercial implementation of graphene-based electronic devices.

Contact Resistance Reduction of WS2 FETs Using High-Pressure Hydrogen Annealing

The transition metal dichalcogenides (TMDCs) have been extensively investigated for various applications such as logic, memory and optical devices, and sensors. The pressing challenge in the research of TMDCs is the electrical performance limited by the high contact resistance. We report more than 5000 times reduction in the contact resistance of WS2 field-effect transistor (FET) with Ti contact (81 M $\Omega ~\mu$ m to 14.6 k $\Omega ~\mu$ m) by high-pressure hydrogen annealing. Schottky barrier height reduction appears to play a major role in the reduction of the contact resistance. This process can be used to reduce the contact resistance even further by combining with a doping technique for TMDCs and a contact metal optimization for TMDC FETs.

Growth and structural characterization of large superconducting crystals of La2−xCa1+xCu2O6

Large crystals of La$_{2-x}$Ca$_{1+x}$Cu$_2$O$_{6}$ (La-Ca-2126) with $x=0.10$ and 0.15 have been grown and converted to bulk superconductors by high-pressure oxygen annealing. The superconducting transition temperature, $T_c$, is as high as 55~K; this can be raised to 60~K by post-annealing in air. Here we present structural and magnetic characterizations of these crystals using neutron scattering and muon spin rotation techniques. While the as-grown, non-superconducting crystals are single phase, we find that the superconducting crystals contain 3 phases forming coherent domains stacked along the $c$ axis: the dominant La-Ca-2126 phase, very thin (1.5 unit-cell) intergrowths of La$_2$CuO$_4$, and an antiferromagnetic La$_8$Cu$_8$O$_{20}$ phase. We propose that the formation and segregation of the latter phases increases the Ca concentration of the La-Ca-2126, thus providing the hole-doping that supports superconductivity.

Strained Germanium Gate-All-Around pMOS Device Demonstration Using Selective Wire Release Etch Prior to Replacement Metal Gate Deposition

Strained Ge p-channel gate-all-around (GAA) devices with Si-passivation are demonstrated on high-density 45-nm active pitch starting from 300-mm SiGe strain relaxed buffer wafers. While single horizontal Ge nanowire (NW) devices are demonstrated, the process flow described in this paper can be adjusted to make vertically stacked horizontal Ge NWs to increase the drive per footprint. The demonstrated short-channel devices have round Ge NWs with 9-nm diameter and are the Ge GAA devices with the smallest channel and gate dimensions (L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">G</sub> = 40 nm) published to date. Electrostatics and off-state leakage are maintained down to the shortest gate lengths studied, showing drain-induced barrier lowering of 30 mV/V and sub20 nA/μm I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</sub> at V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DD</sub> = -0.5 V and L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">G</sub> = 40 nm. The short-channel device subthreshold slope SS and performance can be further improved by use of high-pressure annealing in hydrogen, yielding the best SSLIN and SSSAT of 71 and 76 mV/dec reported so far for any L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">G</sub> = 40-nm Ge pMOS channel device.

Phase transformation in ultrathin Y–Ba–Cu–O films by high-pressure oxygen annealing

To examine the thermodynamic phase stability of Y–Ba–Cu–O superconductors in ultrathin film form, we study the effects of high-pressure oxygen annealing and Cu enrichment on YBa2Cu3O[Formula: see text] films ranging from 8 nm to 15 nm in thickness. The films are grown epitaxially on SrTiO3 substrates by pulsed laser-ablated deposition, and post-annealed in 475 atm of oxygen at 800[Formula: see text]C while subjected to varying concentrations of excess CuO. X-ray diffraction (XRD) on the annealed films shows evidence for suppression of YBa2Cu3O[Formula: see text] and formation of Y2Ba4Cu8O[Formula: see text]. This structural transformation towards a higher-oxidation phase is expectedly correlated with film thinness and Cu enrichment.

OH defects in quartz as monitor for igneous, metamorphic, and sedimentary processes

Oriented sections of more than 500 quartz grains from sediments, igneous, and metamorphic rocks from different localities in Sweden, Austria, Germany, and South Africa were analyzed by FTIR spectroscopy, and their OH defect content was determined with respect to the speciation and total defect water content. Systematic variations of defect speciation and statistical evaluation of total defect contents were used to evaluate the potential of FTIR spectroscopy on quartz as a thermometer in quartzite, as a tool for differentiation trends in granitic systems, and for provenance analysis of sedimentary rocks. In addition to the analyses of natural crystals, high-pressure annealing experiments at lower crustal conditions (1–3 kbar and 650–750 °C) were performed to document the effect of high-grade metamorphism on the defect chemistry. Results indicate that (1) quartz grains from unmetamorphosed granite bodies reveal interesting differentiation trends; (2) sediments and sedimentary rocks are valuable archives to preserve the pre-sedimentary OH defect chemistry, where individual signatures are preserved and can be traced back to potential source rocks; (3) OH defects are retained up to 300 °C over geological time scales; (4) long-term low-grade metamorphic overprint leads to a continuous annealing to lower defect water contents, where Al-specific OH defects survive best; and (5) middle to high-grade annealing drives toward a homogeneous defect partitioning from grain to grain, where the degree of attainment of equilibrium depends on temperature and duration of the thermal event.

Effects of H2 High-pressure Annealing on HfO2/Al2O3/In0.53Ga0.47As Capacitors: Chemical Composition and Electrical Characteristics

We studied the impact of H2 pressure during post-metallization annealing on the chemical composition of a HfO2/Al2O3 gate stack on a HCl wet-cleaned In0.53Ga0.47As substrate by comparing the forming gas annealing (at atmospheric pressure with a H2 partial pressure of 0.04 bar) and H2 high-pressure annealing (H2-HPA at 30 bar) methods. In addition, the effectiveness of H2-HPA on the passivation of the interface states was compared for both p- and n-type In0.53Ga0.47As substrates. The decomposition of the interface oxide and the subsequent out-diffusion of In and Ga atoms toward the high-k film became more significant with increasing H2 pressure. Moreover, the increase in the H2 pressure significantly improved the capacitance‒voltage characteristics, and its effect was more pronounced on the p-type In0.53Ga0.47As substrate. However, the H2-HPA induced an increase in the leakage current, probably because of the out-diffusion and incorporation of In/Ga atoms within the high-k stack.

Tailoring the magnetic properties of nanocrystalline Cu-Co alloys prepared by high-pressure torsion and isothermal annealing

In this study, severe plastic deformation by high-pressure torsion is used as a fabrication method for nanocrystalline magnetic Cu–Co alloys in bulk quantities. By subsequent isothermal annealing, phase separation of the supersaturated solid solutions can be obtained. The magnetic properties of the as-processed and annealed materials have been studied systematically and correlated to the evolving nanostructures investigated in detail by transmission electron microscopy and atom probe tomography. By additional high-pressure torsion deformation at liquid nitrogen temperature the magnetic properties of the Cu74Co26 alloy can be further tuned.

Oriented grain growth and modification of ‘frozen anisotropy’ in the lithospheric mantle

Seismic anisotropy throughout the oceanic lithosphere is often assumed to be generated by fossilized texture formed during deformation at asthenospheric temperatures close to the ridge. Here we investigate the effect of high-temperature and high-pressure static annealing on the texture of previously deformed olivine aggregates to simulate residence of deformed peridotite in the lithosphere. Our experiments indicate that the orientation and magnitude of crystallographic preferred orientation (CPO) will evolve due to the preferential growth of grains with low dislocation densities. These observations suggest that texture and stored elastic strain energy promote a style of grain growth that modifies the CPO of a deformed aggregate. We demonstrate that these microstructural changes alter the orientation distributions and magnitudes of seismic wave velocities and anisotropy. Therefore, static annealing may complicate the inference of past deformation kinematics from seismic anisotropy in the lithosphere.

The phase stability of equiatomic CoCrFeMnNi high-entropy alloy: Comparison between experiment and calculation results

A comparative study about the phase stability of equiatomic CoCrFeMnNi alloy of thermodynamic calculation (Thermo-Calc) and experimental result is shown. The alloy was processed by through a high-pressure torsion (HPT) process and annealing treatment at temperatures ranging from 900 to 600 °C. Phase identification using X-ray diffraction and energy dispersive X-ray spectroscopy indicated that the Cr-rich sigma phase formed during annealing at temperatures lower than 800 °C after the HPT process, and fraction of sigma phase increased as decreasing annealing temperature as predicted by Thermo-Calc. The thermodynamic calculation based on the TCFE database was found to be suitable for predicting the possible phases in the CoCrFeMnNi alloy.

Towards the standardization of graphene growth through carbon depletion, refilling and nucleation

As the graphene is transforming from a laboratory niche material into a mass-produced industrial commodity, maintaining high quality standard across different chemical vapor deposition (CVD) systems becomes the first priority. In this paper, we investigated the carbon diffusion behavior involving two kinds of annealing gases, which reduced the nucleation density in different rate. Compared to the time-consuming and hazardous high-pressure H2 annealing, O2 annealing represents a more efficient route to reduce the nucleation density down to ∼10 nuclei cm−2 in half an hour. We also proposed a well-defined carbon depletion and refilling mechanism, with which we can precisely gauge the minute carbon concentration inside Cu (less than 10 ppm), and control the nucleation density in a reproducible manner. Moreover, we find that O2 displays an impressive carbon depletion activity, ∼6 order more efficient than H2. The graphene single crystals' quality was confirmed with Raman spectroscopy and field effect transistor (FET) devices.

Accessing Forbidden Glass Regimes through High-Pressure Sub-Tg Annealing

Density and hardness of glasses are known to increase upon both compression at the glass transition temperature (Tg) and ambient pressure sub-Tg annealing. However, a serial combination of the two methods does not result in higher density and hardness, since the effect of compression is countered by subsequent annealing and vice versa. In this study, we circumvent this by introducing a novel treatment protocol that enables the preparation of high-density, high-hardness bulk aluminosilicate glasses. This is done by first compressing a sodium-magnesium aluminosilicate glass at 1 GPa at Tg, followed by sub-Tg annealing in-situ at 1 GPa. Through density, hardness, and heat capacity measurements, we demonstrate that the effects of hot compression and sub-Tg annealing can be combined to access a “forbidden glass” regime that is inaccessible through thermal history or pressure history variation alone. We also study the relaxation behavior of the densified samples during subsequent ambient pressure sub-Tg annealing. Density and hardness are found to relax and approach their ambient condition values upon annealing, but the difference in relaxation time of density and hardness, which is usually observed for hot compressed glasses, vanishes for samples previously subjected to high-pressure sub-Tg annealing. This confirms the unique configurational state of these glasses.

High stored energy of metallic glasses induced by high pressure

Modulating energy states of metallic glasses (MGs) is significant in understanding the nature of glasses and controlling their properties. In this study, we show that high stored energy can be achieved and preserved in bulk MGs by high pressure (HP) annealing, which is a controllable method to continuously alter the energy states of MGs. Contrary to the decrease in enthalpy by conventional annealing at ambient pressure, high stored energy can occur and be enhanced by increasing both annealing temperature and pressure. By using double aberration corrected scanning transmission electron microscopy, it is revealed that the preserved high energy, which is attributed to the coupling effect of high pressure and high temperature, originates from the microstructural change that involves “negative flow units” with a higher atomic packing density compared to that of the elastic matrix of MGs. The results demonstrate that HP-annealing is an effective way to activate MGs into higher energy states, and it may assist in understanding the microstructural origin of high energy states in MGs.

Enhanced magnetic refrigeration performance in metamagnetic MnCoSi alloy by high-pressure annealing

MnCoSi alloy exhibits a potential magnetocaloric effect during magnetic field-induced metamagnetic transition. However, the accompanying near-zero entropy change under low magnetic field variation, coupled magnetic hysteresis and poor mechanical properties limit its further application in magnetic refrigeration. In this work, we substantially enhance the magnetic cooling capacity and mechanical performance of stoichiometric MnCoSi alloy via the method of high-pressure annealing. Our results demonstrate that high-pressure annealing can serve as an effective method with which to improve the magnetic cooling capacity of MnCoSi alloy.

Features of the mechanical behavior of ultrafine-grained and nanostructured TiNi alloys

The article presents the results of the study on the mechanical behavior of ultrafine-grained (UFG) and nanocrystalline (NC) TiNi alloys produced by severe plastic deformation (SPD), using the techniques of high pressure torsion (HPT) and annealing. The features of the microstructure and deformation behavior of the NC and UFG alloy have been studied. The amorphous and NC TiNi alloy exhibits enhanced strength. Variation of the post-deformation annealing temperature of the HPT-processed samples can be used for the formation of a structure with various grain sizes and different levels of strength and ductility. Although under deformation the alloy passes to the martensitic state, the dependence of yield stress of TiNi on grain size D in the range of 30 µm to 20 nm (HPT + annealing at 400°C) corresponds to the Hall-Petch relation, and yield stress is determined by the size of the austenite grain.

Phosphorus-doped helical carbon nanofibers as enhanced sensing platform for electrochemical detection of carbendazim.

A combined chemical vapor deposition with high-pressure annealing has been developed for the production of phosphorus-doped helical carbon nanofibers (P-HCNFs). The resulting P-HCNFs have a large specific surface area, well-defined three-dimensional hierarchical helical structure and rapid apparent heterogeneous electron transfer. Based on the high electrocatalytic activity, the P-HCNFs were used to develop an amperometric sensor for carbendazim detection. The experimental results demonstrated that the sensor is promising for the determination of carbendazim in food samples due to the high sensitivity, wide linear range and low detection limit.

Investigation on the high pressure annealing induced re-crystallization mechanism of CH3NH3PbI3 film

In this paper, high pressure annealing induced re-crystallization mechanism of CH3NH3PbI3 film has been investigated by SEM, UV–vis absorption spectra, and X-ray diffraction (XRD), respectively. CH3NH3PbI3 crystals, which were annealed under the pressure of 6 kPa at 100 °C for 80 min, were oriented at the same direction on the surface of the mesoporous Polypropylene (PP) film. These PP/CH3NH3PbI3 composite films exhibited different light-harvesting capabilities over the visible to near-IR. The evolution of the intensity ratio I110/I220 and I220/I310 of CH3NH3PbI3 annealed at 100 °C for different annealing time under the same pressure of 6 kPa has been also investigated in detail. Compared with the film prepared via the traditional method, the high pressure annealing induced CH3NH3PbI3 film showed better stability in moderate humid environmental condition (25% RH).