SnO2: A comprehensive review on structures and gas sensors

A humidity sensor based on a single SnO2 nanowire was fabricated. This sensor has fast and sensitive response to relative humidity (RH) in air from a wide range of atmospheres at 30 °C. The response sensitivity of the sensor to RH is linear to 90%.

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High-Sensitivity Humidity Sensor Based on a Single SnO2 Nanowire

Quasi-one dimensional metal oxide semiconductors: Preparation, characterization and application as chemical sensors

Recent advances in ZnO nanostructures and thin films for biosensor applications: review.

The global demand for data storage and processing has increased exponentially in recent decades. To respond to this demand, research efforts have been devoted to the development of non-volatile memory and neuro-inspired computing technologies. Chalcogenide phase-change materials (PCMs) are leading candidates for such applications, and they have become technologically mature with recently released competitive products. In this Review, we focus on the mechanisms of the crystallization dynamics of PCMs by discussing structural and kinetic experiments, as well as ab initio atomistic modelling and materials design. Based on the knowledge at the atomistic level, we depict routes to improve the parameters of phase-change devices for universal memory. Moreover, we discuss the role of crystallization in enabling neuro-inspired computing using PCMs. Finally, we present an outlook for future opportunities of PCMs, including all-photonic memories and processors, flexible displays with nanopixel resolution and nanoscale switches and controllers. Chalcogenide phase-change materials (PCMs) are leading candidates for non-volatile memory and neuro-inspired computing devices. This Review focuses on the crystallization mechanisms of PCMs as well as the design principles to achieve PCMs with high switching speeds and good data retention, which will aid the development of PCM-based universal memory and neuro-inspired devices.

Designing crystallization in phase-change materials for universal memory and neuro-inspired computing

Ultra-long rutile tin dioxide nanowires and nanobelts are synthesized by thermal oxidation of tin powder using gold film as the catalyst. Nanowire or nanobelts can be selectively produced by tuning the reaction temperature. The vapour-liquid-solid growth mechanism is proposed. The band gaps of the nanowires and nanobelts are 3.74 and 3.81 eV respectively, determined from UV/visible absorption spectral results. The SnO2 nanowires show stable photoluminescence with two emission peaks centred at around 470 and 560 nm. Their wavelengths stay almost fixed while their intensities depend sensitively on the temperatures within the examination ranges from 10 to 300 K. The SnO2 nanobelts show similar photoluminescence behaviours and the origin of the luminescence is discussed.

https://iopscience.iop.org/article/10.1088/0957-4484/17/6/025/pdf

Synthesis and low-temperature photoluminescence properties of SnO2 nanowires and nanobelts.

Rutile (110) tin dioxide nanowires synthesized by thermal oxidation of tin powders and having a band gap of 4.2eV were annealed in vacuum and O2 at 600°C for 1h. The photoluminescence (PL) properties of the as-grown and annealed samples were measured from 10to300K. The nanowires annealed in O2 showed weak luminescence at 393nm at temperatures below 100K, and no luminescence could be detected at temperatures higher than 100K. In contrast, the nanowires annealed in vacuum exhibited strong luminescence at 480nm at temperatures lower than 100K and at 600nm when the temperature was higher than 100K. Our PL results show that the emissions originate from the defect electronic states in the band gap formed by surface oxygen vacancies and solve the long-time controversy over the origin of the luminescence.

Origin of low-temperature photoluminescence from SnO2 nanowires fabricated by thermal evaporation and annealed in different ambients

Although phase change memory technology has developed drastically in the past two decades, the cognition of the key switching materials still ignores an important member, the face-centered cubic Sb2Te3. Apart from the well-known equilibrium hexagonal Sb2Te3 crystal, we prove the metastable face-centered cubic Sb2Te3 phase does exist. Such a metastable crystal contains a large concentration of vacancies randomly occupying the cationic lattice sites. The face-centered cubic to hexagonal phase transformation of Sb2Te3, accompanied by vacancy aggregation, occurs at a quite lower temperature compared to that of Ge2Sb2Te5 alloy. We prove that the covalent-like bonds prevail in the metastable Sb2Te3 crystal, deviating from the ideal resonant features. If a proper doping technique is adopted, the metastable Sb2Te3 phase could be promising for realizing reversibly swift and low-energy phase change memory applications. Our study may offer a new insight into commercialized Ge–Sb–Te systems and help in the design of novel phase change materials to boost the performances of the phase change memory device.

Direct observation of metastable face-centered cubic Sb2Te3 crystal

Surface modification of ceria nanoparticles and their chemical mechanical polishing behavior on glass substrate

In order to decrease the heating temperature of Smart-Cut technology, plasma activation and B+/H+ co-implantation were used. B+/H+ co-implantation gave rise to a decrease of splitting temperature, and finally a high-quality silicon-on-insulator (SOI) structure was fabricated at 300 °C. A diluted Secco etching test indicated that the top Si surface defect density was 104–105 cm−2. An atomic force microscope (AFM) image showed that the surface roughness of the top Si layer was much smaller than that of the SOI structure formed from the H-only implanted wafer. The diluted Secco etching test also indicated that the top Si surface defect density would decrease with the increase of annealing temperature, and 500 °C was a critical temperature for reducing the defect density.

https://iopscience.iop.org/article/10.1088/0268-1242/21/7/022/pdf

Weili Liu

Papers

Synthesis and low-temperature photoluminescence properties of SnO2 nanowires and nanobelts.

Origin of low-temperature photoluminescence from SnO2 nanowires fabricated by thermal evaporation and annealed in different ambients

Direct observation of metastable face-centered cubic Sb2Te3 crystal

Surface modification of ceria nanoparticles and their chemical mechanical polishing behavior on glass substrate

A high-quality SOI structure fabricated by low-temperature technology with B+/H+ co-implantation and plasma bonding