• Proceedings of the Korean Vacuum Society Conference
• /
• 2014.02a
• /
• pp.193.1-193.1
• /
• 2014

This study was to investigate the electronic structure and optical properties of Na doped into NiO thin film using XPS and REELS. The films were grown by electron beam evaporation with varying the annealing temperature. The relationship between the electrical characteristics with the local structure of NiO thin films was also discussed. The x-ray photoelectron results showed that the Ni 2p spectra for all films consist of Ni 2p3/2 which indicate the presence of Ni-O bond from NiO phase and for the annealed film at temperature above $200^{\circ}C$ shows the coexist Ni oxide and Ni metal phase. The reflection electron energy loss spectroscopy spectra showed that the band gaps of the NiO thin films were slightly decreased with Na-doped into films. The Na-doped NiO showed relatively low resistivity compared to the undoped NiO thin films. In addition, the Na-doped NiO thin films deposited at room temperature showed the best properties, such as a p-type semiconducting with low electrical resistivity of $11.57{\Omega}.cm$ and high optical transmittance of ~80% in the visible light region. These results indicate that the Na doping followed by annealing process plays a crucial in enhancing the electrical and optical properties of NiO thin films. We believe that our results can be a good guide for those growing NiO thin films with the purpose of device applications, which require deposited at room temperature.

• Progress in Superconductivity
• /
• v.8 no.1
• /
• pp.27-32
• /
• 2006

[$YBa_2Cu_3O_{7-x}$] thin films were deposited on various buffered-templates by a metal organic chemical vapor deposition(MOCVD). Three different templates of $CeO_2/YSZ/CeO_2/pure-Ni(CYC),\;CeO_2/YSZ/Y_2O_3/Ni-3at.%W(YYC)$ and $CeO_2/IBAD-YSZ$/stainless steel were used. The Ni and Ni-W alloy tapes were biaxially textured by cold rolling and annealing heat treatment. The dense YBCO films were grown on both the IBAD and YYC templates with no microcrack, while the YBCO films on the CYC templates were grown with the formation of microcracks and NiO. The YBCO film on the YYC template showed the higher $I_c$ than that on CYC template. Especially, the IBAD templates with a thin $CeO_2$(type I) and thick $CeO_2$(type II) top layer were used to compare the deposition nature of the YBCO on them. Comparing the current property of the YBCO films on IBAD templates, the YBCO film deposited on thick $CeO_2$ layer was better than the film on thin $CeO_2$ layer.

• Journal of the Korean Electrochemical Society
• /
• v.8 no.1
• /
• pp.32-36
• /
• 2005

[ $WO_3$ ] and $NiO-WO_3$ thin films were deposited on a Si (100) substrate by using high vacuum thermal evaporation. The effects of various film thicknesses on the surface morphology $WO_3$ and $NiO-WO_3$ thin films were investigated. X-ray diffraction (XRD), Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy(XPS) were employed to characterize the deposited films. The results suggest that as $WO_3$ thin films became thick, their grain grew up to a $0.6{\mu}m$. On the other hand, NiO-doping to $WO_3$ thin films inhibited the grain growth five times less than undoped $WO_3$ thin films. This results show that NiO doping inhibited the grain growing of $WO_3$ thin films. Also, the variation of NOx sensitivity $(R_{NOx}/R_{air})$ to the thickness of $WO_3$ and $NiO-WO_3$ thin films were measured according to the thickness change of thin films and the working temperature of sensor in 5ppm NOx gas. As a result, $NiO-WO_3$ thin films showed more excellent properties than $WO_3$ thin films for NOx sensitivity.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.02a
• /
• pp.397-397
• /
• 2013

The electrical, electronic, optical properties and the local structure of Nickel Oxide (NiO) thin film have been investigated by X-ray photoelectron spectroscopy (XPS), Reflection Electron Energy Loss Spectroscopy (REELS), UV-spectrometer,Hall Effect measurement and X-ray absorption spectroscopy (XAS). The XPS results show that the Ni 2p spectra for all films consist of $Ni2p_{3/2}$ at around 854.5 eV which indicate the presence of Ni-O bond from NiO phase and for the annealed film at temperature above $200^{\circ}C$ shows the coexist Ni oxide and Ni metal phase. The REELS spectra showed that the band gaps of the NiO thin films were abruptly decreased with increasing temperature. The values of the band gaps are consistent with the optical band gaps estimated by UV-Spectrometer. The optical transmittance spectra shows that the transparency of NiO thin films in the visible light region was deteriorated with higher temperature due to existence of $Ni^0$. Hall Effect measurement suggest that the NiO thin films prepared at relatively low temperatures (RT and $100^{\circ}C$) are suitable for fabricating p-type semiconductor which showed that the best properties was achieved at $100^{\circ}C$, such as a low resistivity of $7.49{\Omega}.cm$. It can be concluded that the annealing process plays a crucial role in converting from p type to n type semiconductor which leads to reducing electrical resistivity of NiO thin films. Furthermore, the extended X-ray absorption fine structure (EXAFS) spectrum at the Ni K-edge was used to address the local structure of NiO thin films. It was found that the thermal treatments increase the order in the vicinity of Ni atom and lead the NiO thin films to bunsenite crystal structure. Moreover, EXAFS spectra show in increasing of coordination number for the first Ni-O shell and the bond distance of Ni-O with the increase of substrate temperature.

• Korean Journal of Materials Research
• /
• v.14 no.2
• /
• pp.121-125
• /
• 2004

Nickel oxide (NiO) thin films were deposited on Si(100) substrates at room temperature by RF magnetron sputtering from a NiO target. The effects of plasma gas and RF power on the crystallographic orientation and surface morphology of the NiO films were investigated. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM) were employed to characterize the deposited film. It was found that the type of plasma gases affected the crystallographic orientation, deposition rate, surface morphology, and crystallinity of NiO films. Highly crystalline NiO films with (100) orientation were obtained when it was deposited under Ar atmosphere. On the other hand, (l11)-oriented NiO films with poor crystallinity were deposited in $O_2$. Also, the increase in RF power resulted in not only higher deposition rate, larger grain size, and rougher surface but also higher crystallinity of NiO films.

• Applied Microscopy
• /
• v.42 no.4
• /
• pp.207-211
• /
• 2012

We examined the electrical properties and microstructure of NiO produced using a sol-gel method and Ni nitrate hexahydrate ($Ni[NO_3]_2{\cdot}6H_2O$) to investigate if this NiO thin film can be used as an insulator layer for resistance random access memory (ReRAM) devices. It was found that as-prepared NiO film was polycrystalline and presented as the nonstoichiometric compound $Ni_{1+x}O$ with Ni interstitials (oxygen vacancies). Resistances-witching behavior was observed in the range of 0~2 V, and the low-resistance state and high-resistance state were clearly distinguishable (${\sim}10^3$ orders). It was also demonstrated that NiO could be patterned directly by KrF eximer laser irradiation using a shadow mask. NiO thin film fabricated by the sol-gel method does not require any photoresist or vacuum processes, and therefore has potential for application as an insulating layer in low-cost ReRAM devices.

• Journal of the Korean Vacuum Society
• /
• v.19 no.6
• /
• pp.475-482
• /
• 2010

Polycrystalline NiO thin films were deposited on glass substrate by RF magnetron sputtering using only Ar as a plasma sputter gas. based on the analysis of x-ray diffraction (XRD), NiO films had a polycrystalline cubic (NaCl type) structure. NiO thin films grown below and above $200^{\circ}C$ showed preferred orientation of (111) and (220) respectively. It showed colossal change in electrical resistivity as much a ${\sim}10^7$ order form an insulating state of $105\;{\Omega}cm$ below $200^{\circ}C$ to a conducting state of $10^{-2}{\sim}10^{-1}\;{\Omega}cm$ above $300^{\circ}C$ such a Mott metal-insulator transition (MIT) in polycrystalline.

• Current Photovoltaic Research
• /
• v.11 no.2
• /
• pp.39-43
• /
• 2023

Carrier-selective contacts (CSCs) solar cells are considerably attractive on highly efficient crystalline silicon heterojunction (SHJ) solar cells due to their advantages of high thermal tolerance and the simple fabrication process. CSCs solar cells require a hole selective contact (HSC) layer that selectively collects only holes. In order to selectively collect holes, it must have a work function characteristic of 5.0 eV or more when contacted with n-type Si. The VO_x, NiO_x, and CuI_x thin films were fabricated and analyzed respectively to confirm their potential usage as a hole-selective contact (HSC) layer. All thin films showed characteristics of band-gap engergy > 3.0 eV, work function > 5.0 eV and minority carrier lifetime > 1.5 ms.

• Proceedings of the Korean Ceranic Society Conference
• /
• 2000.10a
• /
• pp.190.2-190
• /
• 2000

• Journal of the Korean Chemical Society
• /
• v.65 no.2
• /
• pp.125-132
• /
• 2021

An electrochromic nickel oxide thin film was fabricated on a flexible PET/ITO substrate using a nanocrystallite- dispersed coating sol and bar coater. Nanocrystalline NiOx of 3-4 nm crystallite size was first synthesized by base precipitation and thermal conversion. This NiOx nanocrystallite powder was mechanically dispersed in an alcoholic solvent mixed with a silane binder to prepare a coating sol for thin film. This sol method is different from the normal sol-gel method in that it does not require the conversion of precursor by heat treatment. Therefore, this method provides a very facile method to prepare NiOx thin films on any kind of substrate and it can be easily applied to mass production. The electrochromic performance of this NiOx thin film on PET/ITO electrode with a thickness of about 400 nm was investigated in a nonaqueous LiClO4 electrolyte solution by cyclic voltammetric and repeated chronoamperometric measurements in conjunction with spectrophotometry. The visible light modulation of 44% and the colorization efficiency of 41 ㎠/C at 550 nm were obtained at the step potentials of -0.8/+1.2 V vs Ag and a duration of 30 s.