• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2002년도 제4회 영호남학술대회 논문집
• /
• pp.25-30
• /
• 2002

The ternary semiconducting compounds of the $A_{4}BX_{6}$(A=Cd, Zn, Hg; B=Si, Sn, Ge; X=S, Se, Te) type exhibit strong fluorescence and high photosensitivity in the visible and near infrared ranges, so these are supposed to be materials applicable to photoelectrical devices. These materials were synthesized and single crystals were first grown by Nitsche, who identified the crystal structure of the single crystals. In this paper. author describe the undoped and $Co^{2+}$-doped $Zn_{4}SnSe_{6}$ single crystals were grown by the chemical transport reaction(CTR) method using iodine of $6mg/cm^{3}$ as a transport agent. For the crystal. growth, the temperature gradient of the CTR furnace was kep at $700^{\circ}C$ for the source aone and at $820^{\circ}C$ for the growth zone for 7-days. It was found from the analysis of x-ray diffraction that undoped and $Co^{2+}$-doped $Zn_{4}SnSe_{6}$ compounds have a monoclinic structure. The optical absorption spectra obtained near the fundamental absorption edge showed that these compounds have a direct energy gaps. These temperature dependence of the optical energy gap were closely investigated over the temperature range 10[K]~300[K]

• 반도체디스플레이기술학회지
• /
• 제8권4호
• /
• pp.65-69
• /
• 2009

Carbon nanotubes (CNTs) were coated with undoped zinc oxide (ZnO) or 5 wt% gallium-incorporated ZnO (GZO) using various deposition conditions. The CNTs were directly grown on conical-type tungsten substrates at $700^{\circ}C$ using inductively coupled plasma-chemical vapor deposition. The pulsed laser deposition technique was used to deposit the ZnO and GZO thin films with very low stress. Field-emission scanning electron microscopy and high-resolution transmission electron microscopy were used to monitor the variations in the morphology and microstructure of CNTs prior to and after ZnO or GZO coating. The formation of ZnO and GZO films on CNTs was confirmed using energy-dispersive x-ray spectroscopy. In comparison to the as-grown (uncoated) CNT emitter, the CNT emitter that was coated with a thin (10 nm) GZO film showed remarkably improved field emission characteristics, such as the emission current of $325\;{\mu}A$ at 1 kV and the threshold field of $1.96\;V/{\mu}m$ at $0.1\;{\mu}A$, and it also exhibited the highly stable operation of emission current up to 40 h.

• Transactions on Electrical and Electronic Materials
• /
• 제15권1호
• /
• pp.24-27
• /
• 2014

In this study, the effects of Mn-doping and the electrode materials on the memory characteristics of $ZnO_xS_{1-x}$ resistive random access memory (ReRAM) devices on plastic are investigated. Compared with the undoped Al/$ZnO_xS_{1-x}$/Au and Al/$ZnO_xS_{1-x}$/Cu devices, the Mn-doped ones show a relatively higher ratio of the high resistance state (HRS) to low resistance state (LRS), and narrower resistance distributions in both states. For the $ZnO_xS_{1-x}$ devices with bottom electrodes of Cu, more stable conducting filament paths are formed near these electrodes, due to the relatively higher affinity of copper to sulfur, compared with the devices with bottom electrodes of Au, so that the distributions of the set and reset voltages get narrower. For the Al/$ZnO_xS_{1-x}$/Cu device, the ratio of the HRS to LRS is above $10^6$, and the memory characteristics are maintained for $10^4$ sec, which values are comparable to those of ReRAM devices on Si or glass substrates.

• 한국재료학회지
• /
• 제19권5호
• /
• pp.281-287
• /
• 2009

ZnO thin film was grown on a sapphire single crystal substrate by plasma assisted molecular beam epitaxy. In addition to near band edge (NBE) emissions, both blue and green luminescences are also observed together. The PL intensity of the blue luminescence (BL) range from 2.7 to 2.9 eV increased as the amount of activated oxygen increased, but green luminescence (GL) was weakly observed at about 2.4 eV without much change in intensity. This result is quite unlike previous studies in which BL and GL were regarded as the transition between shallow donor levels such as oxygen vacancy and interstitial zinc. Based on the transition level and formation energy of the ZnO intrinsic defects predicted through the first principle calculation, which employs density functional approximation (DFA) revised by local density approximation (LDA) and the LDA+U approach, the green and blue luminescence are nearly coincident with the transition from the conduction band to zinc vacancies of $V^{2-}_{Zn}$ and $V^-_{Zn}$, respectively.

• 대한전기학회논문지:전기물성ㆍ응용부문C
• /
• 제49권12호
• /
• pp.654-664
• /
• 2000

Thin films of ZnO are deposited by using an RF magnetron sputtering with varying the substrate temperature(RT~39$0^{\circ}C$) and RF power(50~250W). Cu-doped ZnO(denoted by ZnO:Cu) films have also been prepared by co-spputtering of a ZnO target on which some Cu-chips are attached. Different substrate materials, such as Si, $SiO_{2}/Si$, sapphire, DLC/Si, and poly-diamond/Si, are employed to compare the c-axial growth features of deposited ZnO films. Texture coefficient(TC) values for the (002)-preferential growth are estimated from the XRD spectra of deposited films. Optimal ranges of RF powers and substrate temperatures for obtaining high TC values are determined. Effects of Cu-doping conditions, such as relative Cu-chip sputtering areas, $O_{2}/(Ar+O_{2})$ mixing ratios, and reactor pressures, on TC values, electrical resistivities, and relative Cu-compositions of deposited ZnO:Cu films have been systematically investigated. XPS study shows that the relative densities of metallic $Cu(Cu^{0})$ atoms and $CuO(Cu^{2+})$-phases within deposited films may play an important role of determining their electrical resistivities. It should be noted from the experimental results that highly resistive(> $10^{10}{\Omega}cm$ ZnO films with high TC values(> 80%) can be achieved by Cu-doping. SAW devices with ZnO(or Zn):Cu)/IDT/$SiO_{2}$/Si configuration are also fabricated to estimate the effective electric-mechanical coupling coefficient($k_{eff}^{2}$) and the insertion loss. It is observed that the devices using the Cu-doped ZnO films have a higher $k_{eff}^{2}$ and a lower insertion loss, compared with those using the undoped films.

• Current Applied Physics
• /
• 제18권12호
• /
• pp.1465-1472
• /
• 2018

The magnetic and optical properties of Ce-doped ZnO systems have been widely demonstrated, but the effects of different strains of Ce-doped ZnO systems remain unclear. To solve these problems, this study identified the effects of biaxial strain on the electronic structure, absorption spectrum, and magnetic properties of Ce-doped ZnO systems by using a generalized gradient approximation + U (GGA + U) method with plane wave pseudopotential. Under unstrained conditions, the formation energy decreased, the system became stable, and the doping process became easy with the increase in the distances between two Ce atoms. The band gap of the systems with different strains became narrower than that of undoped ZnO without strain, and the absorption spectra showed a red shift. The band gap narrowed, and the red shift became weak with the increase of compressive strain. By contrast, the band gap widened, and the red shift became significant with the increase of tensile strain. The red shift was significant when the tensile strain was 3%. The systems with -1%, 0%, and 1% strains were ferromagnetic. For the first time, the magnetic moment of the system with -1% strain was found to be the largest, and the system showed the greatest beneficial value for diluted magnetic semiconductors. The systems with -3%, -2%, 2%, and 3% strains were non-magnetic, and they had no value for diluted magnetic semiconductors. The ferromagnetism of the system with -1% strain was mainly caused by the hybrid coupling of Ce-4f, Ce-5d, and O-2p orbits. This finding was consistent with Zener's Ruderman-Kittel-Kasuya-Yosida theory. The results can serve as a reference for the design and preparation of new diluted magnetic semiconductors and optical functional materials.

• 한국진공학회지
• /
• 제17권2호
• /
• pp.102-108
• /
• 2008

대향 타겟식 스퍼터링법 (Facing Targets Sputtering)을 이용하여 유리기판위에 증착한 Ag/ZnO 다층 박막의 특성을 연구하였다. Ag 박막의 높은 전도도와 투과율을 나타내는 공정조건을 찾기 위하여, 증착시간, 기판온도 변화에 따른 Ag박막의 특성을 살펴보았으며, ZnO 박막의 두께 변화에 따른 Ag/ZnO 다층박막의 특성을 살펴보았다, 10초간 증착한 Ag 박막은 연속된 막구조를 가지지 못하여, 30초간 증착된 막에 비해 전기적, 광학적 특성이 저하되는 것을 확인할 수 있었다. ZnO 박막의 AFM 측정 결과 박막의 거칠기(Rrms) 값의 변화에 따라 Ag/ZnO박막의 특성에 영향을 미쳤으며, 거칠지 않은 표면을 지닌 박막에서 Ag 박막 증착 시 좋은 특성을 나타냈다. 제작된 박막은 four point probe, UV/VIS spectrometer, AFM을 사용하여 전기적, 광학적, 구조적 특성을 조사하였다. 제작결과 Ag/ZnO 다층박막의 면저항은 9.25 $[\Omega/sq.]$을 나타내었으며, 가시광영역에서 광투과율은 80%이상을 나타내었다.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
• /
• pp.204.2-204.2
• /
• 2013

Wide band gap II-VI semiconductors have attracted the interest of many research groups during the past few years due to the possibility of their applications in light-emitting diodes and laser diodes. Among the II-VI semiconductors, ZnO is an important optoelectronic device material for use in the violet and blue regions because of its wide direct band gap (Eg ~3.37 eV) and large exciton binding energy (60 meV). F-doped ZnO (FZO) and undoped ZnO thin films were grown onto quartz substrate by the sol-gel spin-coating method. The doping level in the solution, designated by F/Zn atomic ratio of was varied from 0 to 5 in 1 steps. To investigate the effects of the structure and optical properties of FZO thin films were investigated using X-ray diffraction (XRD), UV-visible spectroscopy, and photoluminescence (PL). In the XRD, the residual stress, FWHM, bond length, and average grain size were changed with increasing the doping concentration. For the PL spectra, the high INBE/IDLE ratio of the FZO thin films doping concentration at 1 at.% than the other samples.

• 한국진공학회지
• /
• 제13권3호
• /
• pp.109-113
• /
• 2004

InP에서 열처리 온도와 시간 및 활성화 온도에 따른 Zn의 확산의 특성을 electrochemical capacitance-voltage 법으로 조사하였다. InP층은 metal organic chemical vapor deposition를 이용하여 성장하였으며, 화산방법으로는 $Zn_3P_2$ 확산과 박막과 rapid thermal annealing를 사용하였다. 최대의 정공 농도를 갖는 p-lnP 층은 $550^{\circ}C$에서 5분 동안 확산과 활성화를 한 시료에서 얻었고, Zn의 농도는 $1\times10^{19}\textrm{cm}^{-3}$이었다. $550^{\circ}C$에서 5-20 분 동안 확산을 수행한 결과 정공농도의 확산 깊이는 1.51 $\mu\textrm{m}$에서 3.23 $\mu\textrm{m}$로 이동하였고, Zn의 확산계수는 $5.4\times10^{-11}\textrm{cm}^2$/sec이었다. 활성화 시간의 증가로, Zn가 더 깊게 확산하지만, 정공농도는 거의 변화가 없었다. 이는 도핑된 영역의 과잉의 침입형 Zn가 도핑되지 않은 영역으로 빠르게 확산하고 치환형 Zn로 변한다는 것을 의미한다. 정공농도는 $SiO_2$ 박막의 두께가 1,000$\AA$ 이상이어야 안정적으로 분포된다.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1989년도 하계종합학술대회 논문집
• /
• pp.314-318
• /
• 1989

Thin films of undoped and Ga-doped zinc oxide have been prepared by rf sputtering. The films deposited on substrates, which have a columnar structure with the c-axis perpendicular to the substrate surface, consist of very small crystal grains (500-1000 ${\AA}$). Considering doping effects, the electrical resistivity of Ga-doped films decreased by an order of $10^3$ compared to undoped films and the optical transmission was above 80% in the visible range and the optical band gap widened as the Ga content increased.