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

A simple, cost-effective, two-step method was proposed for preparing single-phase SnO polycrystalline thin films on quartz. X-ray diffraction (XRD) analysis demonstrated that the annealed films were consisted of polycrystalline α-SnO phase without preferred orientation, and chemical composition analysis of the single phase in nature was analyzed using X-ray photoelectron spectroscopy (XPS). Transmittance spectra in UV−vis−IR range indicated that the average transmittance of both the as-deposited and the annealed SnO thin films was up to 70%. The optical band gap decreased from 3.20 to 2.77 eV after the annealing process, which was attributed to the crystalline size related quantum size effect. Photoluminescence (PL) spectrum of the annealed film showed only a weak peak at 585 nm, and no intrinsic optical transition emission was observed. Moreover, the p-type conductivity of SnO film was confirmed through Hall effect measurement, with Hall mobility of 1.4 cm2 V−1 s−1 and hole concentration of 2.8 × 1016 cm−3.

Microstructural, Optical, and Electrical Properties of SnO Thin Films Prepared on Quartz via a Two-Step Method

Physical & enhanced photocatalytic properties of green synthesized SnO 2 nanoparticles via Aspalathus linearis

Recently, low temperature solution-processed tin oxide (SnO2) as a versatile electron transport layer (ETL) for efficient and robust planar heterojunction (PH) perovskite solar cells (PSCs) has attracted particular attention due to its outstanding properties such as high optical transparency, high electron mobility, and suitable band alignment. However, for most of the reported works, an annealing temperature of 180 °C is generally required. This temperature is reluctantly considered to be a low temperature, especially with respect to the flexible application where 180 °C is still too high for the polyethylene terephthalate flexible substrate to bear. In this contribution, low temperature (about 70 °C) UV/ozone treatment was applied to in situ synthesis of SnO2 films deposited on the fluorine-doped tin oxide substrate as ETL. This method is a facile photochemical treatment which is simple to operate and can easily eliminate the organic components. Accordingly, PH PSCs with UV-sintered SnO2 films as ETL we...

UV-Sintered Low-Temperature Solution-Processed SnO2 as Robust Electron Transport Layer for Efficient Planar Heterojunction Perovskite Solar Cells

A class of fast response and highly sensitive relative humidity (RH) sensors were developed based on ordered mesoporous SnO2 and Ag/SnO2, which were synthesized via the nanocasting route by directly using mesoporous silica, SBA-15, as hard template. The negative replicated structure of mesoporous SnO2 could provide more channels for transmission of water molecules and charge carriers. Therefore, the nanocasted SnO2 exhibited high humidity sensing performance. The sensitivity of nanocasted mesoporous SnO2 increases 7.5 times than SnO2 synthesized using sodium dodecyl sulfate (SDS), an anionic surfactant. The sensitivity to humidity increased by 5.5 times after adding Ag nanoparticles to nanocasted SnO2. Additionally, the RH sensors show excellent performance with ultra-high sensitivity, fast response/recovery speed, a wide range of RH response, high stability, reversibility and selectivity towards a variety of volatile organic compounds (VOCs) at room temperature. This work could stimulate a right approach to the design of practical humidity sensors with high sensitivity, long stability and fast response.

A facile nanocasting synthesis of mesoporous Ag-doped SnO2 nanostructures with enhanced humidity sensing performance

Large-scale SnO2 nanoblades have been synthesized on a glass substrate covered with a 100-nm-thick SnO2 buffer layer in a controlled aqueous solution at temperatures below 100°C. Typical widths of the nanoblades were about 100–300nm and the lengths were up to 10μm, depending on the growth temperature. The thicknesses were about a few tens of nanometers. Transmission electron microscopy data, x-ray diffraction patterns, and x-ray photoelectron spectroscopy spectral analyses confirmed that the as-grown nanoblades had the phase structure of the rutile form of SnO2 growing along the [110] direction. No other impurities, such as elemental Sn and tin oxides, were detected. An intense blue luminescence centered at a wavelength of 445nm with a full width at half maximum of 75nm was observed in the as-grown SnO2 nanoblades, which is different from the yellow-red light emission observed in SnO2 nanostructures prepared by other methods. It is believed that the strong blue luminescence from the as-grown SnO2 nanoblad...

http://web.nchu.edu.tw/pweb/users/ycho22081/research/5069.pdf

Low-temperature growth and blue luminescence of SnO2 nanoblades

We have studied the dependence of the constituent phases of reactively sputtered AgOx mask layer on the recording and readout mechanisms of super-resolution near-field disk. At low oxygen flow ratios, the AgOx mask layer was found to be composed of an appreciable amount of Ag particles with sizes of tens of nanometers and Ag2O phase. After recording by a high power laser pulse, a hollow Ag cylinder that had its center filled with O2 was formed in the AgOx mask layer. The hollow Ag cylinder would serve as an aperture and could effectively reduce the laser spot size during readout, leading to the super-resolution effect only. At high oxygen flow ratios, the AgOx mask layer was found to be mostly composed of Ag2O and/or AgO phases. After recording by a high power laser pulse, a hollow Ag cylinder that had its center filled with nanosized Ag particles was formed in the AgOx mask layer. The nanosized Ag precipitates would serve as light-scattering centers and could yield strong near-field interaction with the ...

Effect of constituent phases of reactively sputtered AgOx film on recording and readout mechanisms of super-resolution near-field structure disk

The characteristics of several reactively sputtered AgOx films, prepared at different oxygen flow ratios, with and without ZnS-SiO2 protective layers have been examined. For the as-deposited AgOx films, the amount and size of Ag clusters decreased, and the constituent phase of AgOx gradually transferred from pure Ag2O, to a mixture of Ag2O and AgO, then to pure AgO, as the oxygen flow ratio was increased. After annealing, the reduction of AgO into Ag2O and decomposition of Ag2O into Ag and O2 took place, and the decomposed Ag elements would diffuse outward and precipitate small silver particles on the surface of ZnS–SiO2 protective layers. The chemical decomposition of AgOx film confined by ZnS–SiO2 protective layers was confirmed to be an irreversible process. The super-resolution near field effect becomes significant only when the super-resolution near-field structure (super-RENS) disk with an AgOx mask layer prepared at oxygen flow ratios above a threshold value, where AgOx film consists of Ag2O or AgO phase.

http://web.nchu.edu.tw/pweb/users/ycho22081/research/5060.pdf

The Characteristics of Reactively Sputtered AgOx Films Prepared at Different Oxygen Flow Ratios and Its Effect on Super-Resolution Near-Field Properties

Doping Ag into the fast-growth Sb70Te30 recording film can increase the crystallization temperature and activation energy for crystallization so that the archival stability can be improved, however, the initialization will become more difficult. The activation energy for melting of the Ag-doped Sb70Te30 recording films will decrease with Ag concentration so that the recording sensitivity can also be improved. New compounds such as Ag5Te3 and AgSbTe2 will form due to the addition of Ag. When the concentration of Ag was increased, the crystallization mechanisms of the Ag-doped Sb70Te30 recording films will gradually transfer from polyhedral growth to linear growth. Under pulsed laser irradiation, the melt-quenched amorphous zone for the annealed Ag-doped Sb70Te30 recording films will enlarge as the Ag content was increased, representing that the recording sensitivity will increase. However, once the concentration of Ag was increased to 10.8 at. %, the as-deposited Ag-doped Sb70Te30 recording film will become difficult to be initialized.

Thermal-and laser-induced order-disorder switching of Ag-doped fast-growth Sb70Te30 phase-change recording films

The chemical decomposition of AgOx sandwiched between two ZnS–SiO2 protective layers was an irreversible process. We confirmed that a hollow Ag cylinder, or ring, serving as an aperture, was formed and small Ag particles were precipitated in the center region during the recording process. The small aperture can significantly reduce the laser spot size during the readout process and the strong near-field interaction between precipitated Ag particles and subwavelength marks can effectively enhance the readout signal. That clarifies both the super-resolution effect and the near-field interaction in the super-resolution near-field structure disk.

Song-Yeu Tsai

Papers

Low-temperature growth and blue luminescence of SnO2 nanoblades

Effect of constituent phases of reactively sputtered AgOx film on recording and readout mechanisms of super-resolution near-field structure disk

The Characteristics of Reactively Sputtered AgOx Films Prepared at Different Oxygen Flow Ratios and Its Effect on Super-Resolution Near-Field Properties

Thermal-and laser-induced order-disorder switching of Ag-doped fast-growth Sb70Te30 phase-change recording films

Recording and readout mechanisms of super-resolution near-field structure disk with a silver oxide mask layer