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Vacuum Package Using Anodic Bonding Assisted by the Reflow of Low-Melting Temperature Metal
Hoang Manh Chu,Hung Vu Ngoc,하네 카즈히로 한국정밀공학회 2014 International Journal of Precision Engineering and Vol. No.
In this paper, we present a highly effective vacuum seal method, which is based on anodic bonding assisted by the reflow of lowmeltingtemperature metal. To form sacrificial gap for evacuating the packaged cavity before hermetically sealing, the reflow processof Au/Sn/Cr posts due to low-melting temperature Sn metal was introduced. Using this technique to form the evacuation gap, themicro-precise alignment between packaging wafers was obtained. The package method enabled to eliminate contaminant caused bypackage process. The diaphragm structure sensing pressure was used to investigate the proposed package method. The vacuum levelin the packaged cavity was obtained lower than 5 Pa. In comparison to the conventional package method without using the reflowprocess to form the evacuation gap, the vacuum level has been improved by a factor of 8. The yield and uniformity of the packagemethod were also confirmed to be higher than the conventional package method without using the reflow process to form theevacuation gap. This vacuum package method can be implemented to remove air damping for optimal performance of mechanicaloscillators such as accelerometers, gyroscopes, energy harvesters, and micro-mirrors.
Van Hoang, Nguyen,Hung, Chu Manh,Hoa, Nguyen Duc,Van Duy, Nguyen,Park, Inkyu,Van Hieu, Nguyen Elsevier Sequoia 2019 Sensors and actuators. B Chemical Vol.282 No.-
<P><B>Abstract</B></P> <P>Cost-effective fabrication of sensors and detection of ultralow concentrations of toxic gases are important concerns for environmental monitoring. In this study, the reduced graphene oxide (RGO)-loaded ZnFe<SUB>2</SUB>O<SUB>4</SUB> nanofibers (ZFO-NFs) were fabricated by facile on-chip electrospinning method and subsequent heat treatment. The multi-porous NFs with single-phase cubic spinel structure and typical spider-net morphology were directly assembled on Pt-interdigitated electrodes. The diameters of the RGO-loaded ZFO-NFs were approximately 50–100 nm with many nanograins. The responses to H<SUB>2</SUB>S gas showed a bell-shaped behaviour with respect to RGO contents and annealing temperatures. The optimal values of the RGO contents and the annealing temperatures were found to be about 1.0 wt% and 600 °C, respectively. The response of the RGO-loaded ZnFe<SUB>2</SUB>O<SUB>4</SUB> NFs to 1 ppm H<SUB>2</SUB>S gas was as high as 147 at 350°C while their cross-gas responses to SO<SUB>2</SUB> (10 ppm), NH<SUB>3</SUB> (100 ppm), H<SUB>2</SUB> (250 ppm), C<SUB>3</SUB>H<SUB>6</SUB>O (1000 ppm), and C<SUB>2</SUB>H<SUB>5</SUB>OH (1000 ppm) were rather low (1.8−5.6). The high sensor response was attributed to formation of a heterojunction between RGO and ZnFe<SUB>2</SUB>O<SUB>4</SUB> and due to the fact that NFs consisted of many nanograins which resulted in multi-porous structure and formation of potential barriers at grain boundaries.</P> <P><B>Highlights</B></P> <P> <UL> <LI> rGO-loaded ZnFe<SUB>2</SUB>O<SUB>4</SUB> nanofibers have simply prepared by electrospinning. </LI> <LI> rGO-loaded ZnFe<SUB>2</SUB>O<SUB>4</SUB> nanofiber sensors can detect H<SUB>2</SUB>S gas down to ppb level. </LI> <LI> The loading rGO can result in an enhancement of H<SUB>2</SUB>S gas ensing performance. </LI> </UL> </P>
Close-Packed Monolayer Self-Assembly of Silica Nanospheres Assisted by Infrared Irradiation
Nguyen Van Minh,Nguyen Thi Hue,Nghiem Thi Ha Lien,Chu Manh Hoang 대한금속·재료학회 2018 ELECTRONIC MATERIALS LETTERS Vol.14 No.1
In this paper, we report on a fast and cost-effective dropcoating technique for the self-assembly of silica nano-spheresfrom a mono-dispersed colloidal suspension into close-packedmonolayer (CMP) on hydrophilic single-crystal siliconsubstrate. The technique includes the self-assembly of silicanano-spheres on slanted silicon substrate and infraredirradiation during evaporation process of the coated droplet. The influence of the substrate slant angle and infraredirradiation on the formation of silica nano-sphere monolayer isinvestigated. This achievement is promising for variousapplications, such as a mask layer for nano-sphere lithographythat is employed for producing fundamental elements inphotonics, plasmonics, and solar cell.