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Phase-controlled growth of cobalt oxide thin films by atomic layer deposition
Jung, Soonyoung,Nandi, Dip K.,Yeo, Seungmin,Kim, Hyungjun,Jang, Yujin,Bae, Jong-Seong,Hong, Tae Eun,Kim, Soo-Hyun Elsevier Sequoia 2018 Surface & coatings technology Vol.337 No.-
<P><B>Abstract</B></P> <P>Cobalt oxide (CoO<SUB>x</SUB>) thin films were deposited on thermally grown SiO<SUB>2</SUB> substrates by atomic layer deposition (ALD) using bis(1,4-di-iso-propyl-1,4-diazabutadiene)cobalt (C<SUB>16</SUB>H<SUB>32</SUB>N<SUB>4</SUB>Co) and oxygen (O<SUB>2</SUB>) as reactants at deposition temperatures ranging from 125 to 300 °C. X-ray diffraction (XRD) and Raman spectroscopic analysis indicated that a mixed-phase oxide consisting of CoO and Co<SUB>3</SUB>O<SUB>4</SUB> was deposited at temperatures ranging from 125 to 250 °C. However, single-phase Co<SUB>3</SUB>O<SUB>4</SUB> was deposited above the deposition temperature of 275 °C. Further, analyses by Rutherford backscattering spectrometry, transmission electron microscopy, and selected area electron diffraction along with XRD and Raman spectroscopy revealed that the single-phase cobalt oxide film was stoichiometric crystalline (spinel structure) with negligible N and C impurities. The optical band gap of the single-phase Co<SUB>3</SUB>O<SUB>4</SUB> film was 1.98 eV and increased with decreasing deposition temperature. It was also shown that the mixed-phase cobalt oxide thin films could be converted into single-phase spinel Co<SUB>3</SUB>O<SUB>4</SUB> by annealing at 350 °C in O<SUB>2</SUB> ambient. It was further observed that the phase of the ALD-grown cobalt oxide thin film could be controlled by controlling the precursor or reactant pulsing condition. The study revealed that pure Co<SUB>3</SUB>O<SUB>4</SUB> phase could be grown at a relatively low temperature (250 °C) by using water vapor as a reactant. Therefore, this work systemically demonstrated several pathways to grow single-phase Co<SUB>3</SUB>O<SUB>4</SUB> by ALD using a novel metalorganic cobalt precursor.</P> <P><B>Highlights</B></P> <P> <UL> <LI> ALD grown single-phase Co<SUB>3</SUB>O<SUB>4</SUB> using O<SUB>2</SUB> molecules at 275 °C </LI> <LI> A high growth rate of 0.808 nm/cycle </LI> <LI> Stoichiometric and crystalline ALD-Co<SUB>3</SUB>O<SUB>4</SUB> with an optical bandgap of 1.98 eV </LI> <LI> Tuning of optical bandgaps and phases with the deposition temperature </LI> </UL> </P>
안순영(Soonyoung Ahn),김기덕(Ki Deog Kim),이종남(Jong Nam Lee),임주성(Ju Sung Im),남춘우(Chun Woo Nam),정진철(Jin Chel Jung),이응호(Eung Ho Lee) 한국원예학회 2008 원예과학기술지 Vol.26 No.4
This study was conducted to examine the removal efficiency of 4 pesticides in Chinese cabbage (Brassica campestris L.) by different types of washing solution after harvest. To determine the removal efficiency of different washing solutions, samples were stored at 4℃, washed by different washing solutions and analyzed for amount of pesticide residues in Chinese cabbage. Removal efficiency of pesticide by tap water, baking soda (0.2%), charcoal water (20 g?L<SUP>-1</SUP>, pH 7.2), vinegar (5%) ranged from 26.5-83.8%, 32.7-93.3%, 40.3-89.7%, and 22.9-85.1%, respectively. The order of average removal efficiency of the pesticides was bifenthrin (82.7%), kresoxim-methyl (79.7%), pyraclofos (44.4%) and metalaxyl (38.2%). The washing efficiency of a pesticide is not correlated with its water solubility.
Taeju Lee,Soonyoung Hong,Chongsoo Jung,Junghyup Lee,Minkyu Je 대한전자공학회 2019 Journal of semiconductor technology and science Vol.19 No.1
This paper presents a fully differential implantable neural recording front-end IC for monitoring neural activities. Each analog front-end (AFE) consists of a low-noise amplifier (LNA), a variable gain amplifier (VGA), and a buffer. The output signal of the AFE is digitized through a successive approximation register analog-to-digital converter (SAR ADC). The LNA adopts the currentreuse technique to improve the current efficiency, achieving the power consumption as low as 0.95 μW. The implemented LNA has the gain of 40 dB, the lowpass cutoff frequency of 10 kHz, and the high-pass cutoff frequency of sub-1 Hz which is realized using the current-controlled pseudoresistor. The VGA controls the gain from 21.9 dB to 33.9 dB for efficient digitization while consuming the power of 0.35 μW. The buffer drives the capacitive DAC of the ADC and consumes the power of 3.28 μW. The fabricated AFE occupies the area of 0.11 ㎟/Channel and consumes 4.6 μW/Channel under 1-V supply voltage. Each channel achieves the input-referred noise of 2.88 μVrms, the NEF of 2.38, and the NEF²VDD of 5.67. The front-end IC is implemented in a standard 1P6M 0.18-mm CMOS process.