MoO_x 기반의 고성능 투명 광검출기

박왕희,이경남,김준동,Park, Wang-Hee,Lee, Gyeongnam,Kim, Joondong 한국전기전자재료학회 2017 전기전자재료학회논문지 Vol.30 No.6

A high-performing all-transparent photodetector was created by configuring a $MoO_x$/NiO/ZnO/ITO structure on a glass substrate. The ITO bottom layer was applied as a back contact. To achieve the transparent p/n junction, p-type NiO was coated on the n-type ZnO layer. Reactive sputtering was used to spontaneously form the ZnO or NiO layer. In order to improve the transparent photodetector performance, the functional $MoO_x$ window layer was used. Optically, the $MoO_x$ window provided a refractive index layer (n=1.39) lower than that of NiO (n=2), increasing the absorption of the incident light wavelengths (${\lambda}s$). Moreover, the $MoO_x$ window can provide a lower sheet resistance to improve the carrier collection for the photoresponses. The $MoO_x$/NiO/ZnO/ITO device showed significantly better photoresponses of 877.05 (at ${\lambda}$=460nm), 87.30 (${\lambda}$=520 nm), and 30.38 (${\lambda}$=620 nm), compared to 197.28 (${\lambda}$=460 nm), 51.74 (${\lambda}$=520 nm) and 25.30 (${\lambda}$=620 nm) of the NiO/ZnO/ITO device. We demonstrated the high-performing transparent photodetector by using the multifunctional $MoO_x$ window layer.

Volatile organic compound sensing properties of MoO₃–ZnO core–shell nanorods

Lee, Wan In,Bonyani, Maryam,Lee, Jae Kyung,Lee, Chongmu,Choi, Seung-Bok ELSEVIER 2018 CURRENT APPLIED PHYSICS Vol.18 No.supp

<P>MoO3-ZnO core-shell nanorods were synthesized by a simple two-step process. MoO3 nanorods were synthesized by a hydrothermal method, which was followed by atomic layer deposition of a ZnO shell. The phase and crystallinity of the synthesized products were examined by X-ray diffraction, and the morphological features were studied by scanning electron microscopy. Gas sensing tests were performed on both pristine MoO3 nanorods and MoO3-ZnO core-shell nanorods. Sensors containing the pristine MoO3 nanorods and MoO3-ZnO core-shell nanorods showed responses (R-a/R-g where R-a and R-g are the electrical resistances of the sensors in air and the target gas, respectively) of 1.15 and 7.6, respectively, to 200 ppm ethanol at 350 degrees C. Therefore, the response of the MoO3-ZnO core-shell nanorod sensors to ethanol gas was significantly better than that of pristine MoO3 nanorods. The underlying mechanisms for the enhanced sensing performance are discussed in detail. (C) 2017 Elsevier B.V. All rights reserved.</P>

Photocatalytic effect of TiO₂-coated CaLa₂(MoO₄)₄ and CaLa₂(MoO₄)₄:Er/Yb nano core–shells and upconversion photoluminescence properties of CaLa₂(MoO<sub>4</sub

Oh, Won-Chun,Ye, Shu,Park, Jung Gyu,Kang, Suk Hyun,Lim, Chang Sung Elsevier 2015 Journal of industrial and engineering chemistry Vol.32 No.-

<P><B>Abstract</B></P> <P>TiO<SUB>2</SUB>-coated CaLa<SUB>2</SUB>(MoO<SUB>4</SUB>)<SUB>4</SUB> and CaLa<SUB>2</SUB>(MoO<SUB>4</SUB>)<SUB>4</SUB>:Er/Yb nano core–shells were successfully synthesized using two-step procedures of the microwave sol–gel and ultrasonic methods. Well-crystallized nano core–shells showed a fine and homogeneous morphology with particle sizes of 10–20nm. The degradation efficiency for TiO<SUB>2</SUB>-coated CaLa<SUB>2</SUB>(MoO<SUB>4</SUB>)<SUB>4</SUB> and CaLa<SUB>1.7</SUB>(MoO<SUB>4</SUB>)<SUB>4</SUB>:Er<SUB>0.1</SUB>Yb<SUB>0.2</SUB> under visible light resulted in the order as 10>15>5wt%. Under excitation at 980nm, the upconversion intensities of CaLa<SUB>1.7</SUB>(MoO<SUB>4</SUB>)<SUB>4</SUB>:Er<SUB>0.1</SUB>Yb<SUB>0.2</SUB> and CaLa<SUB>1.5</SUB>(MoO<SUB>4</SUB>)<SUB>4</SUB>:Er<SUB>0.05</SUB>Yb<SUB>0.45</SUB> particles exhibited a strong 525nm and a weak 550nm emission bands in the green region. The CIE diagram showed a good match with yellowish green emissions.</P> <P><B>Highlights</B></P> <P> <UL> <LI> TiO<SUB>2</SUB>-coated CaLa<SUB>2</SUB>(MoO<SUB>4</SUB>)<SUB>4</SUB>:Er/Yb nano core–shells were made by two-step methods. </LI> <LI> Nano core–shells showed a fine morphology with particle sizes of 10–20nm. </LI> <LI> 10wt% TiO<SUB>2</SUB>-coated CaLa<SUB>2</SUB>(MoO<SUB>4</SUB>)<SUB>4</SUB>:Er/Yb provided the best photocatalytic effect. </LI> <LI> UC intensities exhibited a strong 525nm and a weak 550nm emission bands. </LI> <LI> The CIE color coordinates showed a good match with yellowish green emissions. </LI> </UL> </P>

Fabrication and characterization of Yb/MoO3/(C,Yb) devices

S.E. Al Garni,A.F. Qasrawi 한국물리학회 2019 Current Applied Physics Vol.19 No.4

In this study we have explored some of the properties of Yb/MoO3/(C, Yb) thin films as a multifunctional optoelectronic device. While the MoO3 films which are deposited onto glass substrate are found to be of amorphous nature, the Yb metal induced the growth of orthorhombic phase of MoO3. The films are high transparent and exhibit energy band gap value of 3.0 eV which make it sensitive to light signals in the near ultraviolet range of light. In addition, the frequency dependent capacitance-voltage characteristics of Yb/MoO3/ (C,Yb) structure display pronounced accumulation, depletion and inversion regions that nominate it for use as tunable metal-oxide-semiconductor MOS device. The physical parameters including the built in voltage, barrier height, flat band and threshold voltages of the MOS capacitors are also determined. Furthermore, the currentvoltage characteristics displayed high rectification ratio that could reach 1.26×104 at biasing voltage of 0.5 V nominating the Yb/MoO3/C device for use as electronic switches. On the other hand, the impedance spectroscopy analysis in the frequency domain of 0.01–1.80 GHz, have shown that the Yb/MoO3/Yb structures are more appropriate for microwave applications than Yb/MoO3/C device. The microwave cutoff frequency for the Yb sandwiched MoO3 exceeds 140 GHz. The return loss for the Yb/MoO3/Yb reaches 26 dB at 1.8 GHz. These values are attractive as they suit microwave low/high pass band filters.

Reductive-annealing-induced changes in Mo valence states on the surfaces of MoO3 single crystals and their high temperature transport

공현준,권한솔,김혜경,진광수,이재광,이준혁,허윤석,조진형,진형진 한국물리학회 2019 Current Applied Physics Vol.19 No.12

Reduction of MoO3 in extreme reducing condition is a way to achieve Mo metal. However, effect of less extreme reductive-annealing, where it allows to keep the crystal structure, on physical and chemical properties of MoO3 has not been well-studied. In this work, we studied the evolution of Mo valence state during reductive annealing and its effect on high temperature transport. We found the formation of oxygen vacancies on surface of MoO3 single crystals at the low temperature, which is evidenced by increase of Mo5+ and color change. In addition, formation of Mo4+ was at the elevated temperature. For understanding the relation between bulk conductivity and Mo valence state, real-time impedance spectroscopy is employed. Use of two different gases makes it possible to distinguish impedance responses of MoO3 from those of reduced MoO3-x. Also, from time-dependent impedance measurements, we observed the evolution of transport behaviour by evolution of Mo valence state.

원자층 증착법으로 증착된 MoO_x를 적용한 전하 선택 접합의 이종 접합 태양전지

정민지,조영준,이선화,이준신,임경진,서정호,장효식,Jeong, Min Ji,Jo, Young Joon,Lee, Sun Hwa,Lee, Joon Shin,Im, Kyung Jin,Seo, Jeong Ho,Chang, Hyo Sik 한국재료학회 2019 한국재료학회지 Vol.29 No.5

Hole carrier selective MoOx film is obtained by atomic layer deposition(ALD) using molybdenum hexacarbonyl[$Mo(CO)_6$] as precursor and ozone($O_3$) oxidant. The growth rate is about 0.036 nm/cycle at 200 g/Nm of ozone concentration and the thickness of interfacial oxide is about 2 nm. The measured band gap and work function of the MoOx film grown by ALD are 3.25 eV and 8 eV, respectively. X-ray photoelectron spectroscopy(XPS) result shows that the $Mo^{6+}$ state is dominant in the MoOx thin film. In the case of ALD-MoOx grown on Si wafer, the ozone concentration does not affect the passivation performance in the as-deposited state. But, the implied open-circuit voltage increases from $576^{\circ}C$ to $620^{\circ}C$ at 250 g/Nm after post-deposition annealing at $350^{\circ}C$ in a forming gas ambient. Instead of using a p-type amorphous silicon layer, high work function MoOx films as hole selective contact are applied for heterojunction silicon solar cells and the best efficiency yet recorded (21 %) is obtained.

Comparative Study of Undoped and Nickel-Doped Molybdenum Oxide Photoanodes for PEC Water Splitting

Garcia-Garcia, Matias The Korean Electrochemical Society 2022 Journal of electrochemical science and technology Vol.13 No.3

The current global energy supply depends heavily on fossil fuels. This makes technology such as direct water splitting from harvesting solar energy in photoelectrochemical (PEC) systems potentially attractive due to its a promising route for environmentally benign hydrogen production. In this study, undoped and nickel-doped molybdenum oxide photoanodes (called photoanodes S₁ and S₂ respectively) were synthesized through electrodeposition by applying -1.377 V vs Ag/AgCl (3 M KCl) for 3 hours on an FTO-coated glass substrate immersed in molibdatecitrate aqueous solutions at pH 9. Scanning electron microscopy (SEM), atomic force microscopy (AFM), energy-dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS) were used for microstructural and compositional characterizations of the photoanodes. In addition, the optical and photoelectrochemical characterizations of these photoanodes were performed by UV-Visible spectroscopy, and linear scanning voltammetry (LSV) respectively. The results showed that all the photoanodes produced exhibit conductivity and catalytic properties that make them attractive for water splitting application in a photoelectrochemical cell. In this context, the photoanode S₂ exhibited better photocatalytic activity than the photoanode S₁. In addition, photoanode S₂ had the lowest optical band-gap energy value (2.58 eV), which would allow better utilization of the solar spectrum.

MoO<SUB>x</SUB>를 사용한 청색 형광 Tandem OLED의 발광 특성

곽태호(Tea-Ho Kwak),주성후(Sung-Hoo Ju) 한국표면공학회 2014 한국표면공학회지 Vol.47 No.3

To improve emission efficiency of organic light emitting devices (OLEDs), we fabricated the tandem OLED of ITO / 2-TNATA / NPB / SH-1: 3 vol.% BD-2 / Bphen / Liq / Al / MoOx (X nm) / 2-TNATA / NPB / SH-1: 3 vol.% BD-2 / Bphen / Liq / Al structure. And emission properties of single OLED and tandem OLED with MoOx thickness as charge generation layer (CGL) were measured. The current emission efficiency and quantum efficiency of tandem OLED with MoOx of 3 nm thickness were improved compare with single OLED from 7.46 cd/A and 5.39% to 22.57 cd/A and 11.76%, respectively. In case of thicker or thinner than MoOx of 3~5 nm, the current emission efficiency and quantum efficiency were decreased, because balance of electron and hole in emission layer was not matching. The driving voltage was increased from 8 V of single OLED to 15 V of tandem OLED by thickness increase of OLED. As a result, it was possible to improve the emission efficiency of OLEDs by optimized MoOx thickness.

Soft X-ray Spectroscopy of C60/Copper Phthalocyanine/MoO3 interfaces: Role of reduced MoO3 on energetic band alignment and improved performance

정현경,강희재,박준호,김주혁,여소령,조상완 한국진공학회 2019 한국진공학회 학술발표회초록집 Vol.2019 No.8

PE-ALD를 이용하여 증착한 MoO<SUB>x</SUB>의 특성

임태완,장효식 한국진공학회 2019 한국진공학회 학술발표회초록집 Vol.2019 No.2