Effect of Thermal Annealing on the SAW Properties of AlN Films Deposited on Si Substrate

Hoang-Si Hong,Gwiy-Sang Chung* 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.54 No.4

This paper aims to describe the influence of a long post-deposition heat treatment on the surface acoustic wave (SAW) properties of polycrystalline (poly) aluminum-nitride (AlN) thin films by investigating changes in the surface morphology and stress on the films. The poly-AlN thin lms with a (002) preferred orientation were deposited on silicon (Si) substrates by using a pulsed reactive magnetron sputtering system. The SAW velocity and insertion loss were improved slightly after annealing at 600℃ and were worse for the lms annealed at 900 ℃. The change in film quality was not significant enough to strongly improve the SAW properties. In addition, the experimental relationship between insertion loss and the geometrical structures of two-port SAW resonators was investigated. The results were measured by using a network analyzer and showed that the number of inter-digital transducer (IDT) nger pairs (N), the number of reflector grating pairs (R), the IDT center-to-center distance (L) and the wavelength (λ) were all related to the insertion loss. The best insertion loss result was about 15.6 dB for the SAW resonator with R = 160 pairs, N = 5 pairs, L = 750μm and λ = 50 μm. The characteristics of AlN thin films were also evaluated using Fourier transform-infrared spectroscopy (FT-IR) spectra and X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM) images. This paper aims to describe the influence of a long post-deposition heat treatment on the surface acoustic wave (SAW) properties of polycrystalline (poly) aluminum-nitride (AlN) thin films by investigating changes in the surface morphology and stress on the films. The poly-AlN thin lms with a (002) preferred orientation were deposited on silicon (Si) substrates by using a pulsed reactive magnetron sputtering system. The SAW velocity and insertion loss were improved slightly after annealing at 600℃ and were worse for the lms annealed at 900 ℃. The change in film quality was not significant enough to strongly improve the SAW properties. In addition, the experimental relationship between insertion loss and the geometrical structures of two-port SAW resonators was investigated. The results were measured by using a network analyzer and showed that the number of inter-digital transducer (IDT) nger pairs (N), the number of reflector grating pairs (R), the IDT center-to-center distance (L) and the wavelength (λ) were all related to the insertion loss. The best insertion loss result was about 15.6 dB for the SAW resonator with R = 160 pairs, N = 5 pairs, L = 750μm and λ = 50 μm. The characteristics of AlN thin films were also evaluated using Fourier transform-infrared spectroscopy (FT-IR) spectra and X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM) images.

High-sensitivity humidity sensors with ZnO nanorods based two-port surface acoustic wave delay line

Hong, Hoang-Si,Phan, Duy-Thach,Chung, Gwiy-Sang Elsevier 2012 Sensors and actuators. B, Chemical Vol.171 No.-

Effect of a 3C-SiC Buffer Layer on the SAW Properties of AlN Films Grown on Si Substrates

정귀상,Hoang-Si Hong 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.4

This paper aims to describe the influence of a polycrystalline (poly) 3C-SiC buffer layer on the surface acoustic wave (SAW) properties of poly aluminum nitride (AlN) thin films by comparing the center frequency, the insertion loss, the electromechanical coupling coefficient (k2), and the temperature coefficient of frequency (TCF) of an inter-digital transducer (IDT)/AlN/3C-SiC structure with those of an IDT/AlN/Si structure. The poly-AlN thin films with a (0002) preferred orientation were deposited on silicon (Si) substrates by using a pulsed reactive magnetron sputtering system. Experimental results show that the insertion loss (21.92 dB) and the TCF (−18 ppm/˚C) of the IDT/AlN/3C-SiC structure were improved because of the closely-matched coefficients of thermal expansion (CTE) and the small lattice mismatch (1%) between AlN and 3C-SiC. However, the drawback is that the k2(0.79%) and the SAW velocity (5020 m/s) of the AlN/3C-SiC SAW device are reduced by the appearance of some non-(0002) AlN planes, such as (1012) and (1013) AlN planes, in the AlN/SiC film. Although disadvantages still exist, the use of the AlN/3C-SiC structure for SAW applications at high temperatures is suitable. The characteristics of the AlN thin films were also evaluated using Fourie transform infrared spectra and both X-ray diffraction and atomic force microscopy images. This paper aims to describe the influence of a polycrystalline (poly) 3C-SiC buffer layer on the surface acoustic wave (SAW) properties of poly aluminum nitride (AlN) thin films by comparing the center frequency, the insertion loss, the electromechanical coupling coefficient (k2), and the temperature coefficient of frequency (TCF) of an inter-digital transducer (IDT)/AlN/3C-SiC structure with those of an IDT/AlN/Si structure. The poly-AlN thin films with a (0002) preferred orientation were deposited on silicon (Si) substrates by using a pulsed reactive magnetron sputtering system. Experimental results show that the insertion loss (21.92 dB) and the TCF (−18 ppm/˚C) of the IDT/AlN/3C-SiC structure were improved because of the closely-matched coefficients of thermal expansion (CTE) and the small lattice mismatch (1%) between AlN and 3C-SiC. However, the drawback is that the k2(0.79%) and the SAW velocity (5020 m/s) of the AlN/3C-SiC SAW device are reduced by the appearance of some non-(0002) AlN planes, such as (1012) and (1013) AlN planes, in the AlN/SiC film. Although disadvantages still exist, the use of the AlN/3C-SiC structure for SAW applications at high temperatures is suitable. The characteristics of the AlN thin films were also evaluated using Fourie transform infrared spectra and both X-ray diffraction and atomic force microscopy images.

Characteristics of SAW humidity sensor using nanocrystalline ZnO films

황시홍 ( Hoang Si Hong ),정귀상 ( Gwiy Sang Chung ) 한국센서학회 2010 센서학회지 Vol.19 No.5

Facile synthesis of SnO2eZnO coreeshell nanowires for enhanced ethanol-sensing performance

Dang Thi Thanh Le,Do Dang Trung,Nguyen Duc Chinh,Bui Thi Thanh Binh,Hoang Si Hong,Nguyen Van Duya,Nguyen Duc Hoa,Nguyen Van Hieu 한국물리학회 2013 Current Applied Physics Vol.13 No.8

The design of coreeshell heteronanostructures is powerful tool to control both the gas selectivity and the sensitivity due to their hybrid properties. In this work, the SnO2eZnO coreeshell nanowires (NWs) were fabricated via two-step process comprising the thermal evaporation of the single crystalline SnO2 NWs core and the spray-coating of the grainy polycrystalline ZnO shell for enhanced ethanol sensing performance. The as-obtained products were investigated by X-ray diffraction, scanning electron microscopy,and photoluminescence. The ethanol gas-sensing properties of pristine SnO2 and ZnOeSnO2 core eshell NW sensors were studied and compared. The gas response to 500 ppm ethanol of the coreeshell NW sensor increased to 33.84, which was 12.5-fold higher than that of the pristine SnO2 NW sensor. The selectivity of the coreeshell NW sensor also improved. The response to 100 ppm ethanol was about 14.1,whereas the response to 100 ppm liquefied petroleum gas, NH3, H2, and CO was smaller, and ranged from 2.5 to 5.3. This indicates that the coreeshell heterostructures have great potential for use as gas sensing materials.

Deciphering the DNA methylation landscape of colorectal cancer in a Korean cohort

Seok-Byung Lim,Soobok Joe,Hyo-Ju Kim,Jong Lyul Lee,In Ja Park,Yong Sik Yoon,Chan Wook Kim,Jong Hwan Kim,Sangok Kim,Jin-Young Lee,Hyeran Shim,Hoang Bao Khanh Chu,Sheehyun Cho,Jisun Kang,Si-Cho Kim,Hong 생화학분자생물학회 2023 BMB Reports Vol.56 No.10

Aberrant DNA methylation plays a pivotal role in the onsetand progression of colorectal cancer (CRC), a disease with highincidence and mortality rates in Korea. Several CRC-associateddiagnostic and prognostic methylation markers have been identified;however, due to a lack of comprehensive clinical andmethylome data, these markers have not been validated in theKorean population. Therefore, in this study, we aimed to obtainthe CRC methylation profile using 172 tumors and 128 adjacentnormal colon tissues of Korean patients with CRC. Based onthe comparative methylome analysis, we found that hypermethylatedpositions in the tumor were predominantly concentratedin CpG islands and promoter regions, whereas hypomethylatedpositions were largely found in the open-sea region,notably distant from the CpG islands. In addition, we stratifiedpatients by applying the CpG island methylator phenotype(CIMP) to the tumor methylome data. This stratification validatedprevious clinicopathological implications, as tumors with highCIMP signatures were significantly correlated with the proximalcolon, higher prevalence of microsatellite instability status, andMLH1 promoter methylation. In conclusion, our extensive methylomeanalysis and the accompanying dataset offers valuableinsights into the utilization of CRC-associated methylation markersin Korean patients, potentially improving CRC diagnosis andprognosis. Furthermore, this study serves as a solid foundationfor further investigations into personalized and ethnicity-specificCRC treatments.