• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.446-446
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• 2011

One dimensional (1-D) structures of ZnO nanorods are promising elements for future optoelectronic devices. However there are still many obstacles in fabricating high-quality p-type ZnO up to now. In addition, it is limited to measure the degree of the doping concentration and carrier transport of the doped 1-D ZnO with conventional methods such as Hall measurement. Here we demonstrate the measurement of the electronic properties of p- and n-doped ZnO nanorods by the Kelvin probe force microscopy (KPFM). Vertically aligned ZnO nanorods with intrinsic n-doped, As-doped p-type, and p-n junction were grown by vapor phase epitaxy (VPE). Individual nanowires were then transferred onto Au films deposited on Si substrates. The morphology and surface potentials were measured simultaneously by the KPFM. The work function of the individual nanorods was estimated by comparing with that of gold film as a reference, and the doping concentration of each ZnO nanorods was deduced. Our KPFM results show that the average work function difference between the p-type and n-type regions of p-n junction ZnO nanorod is about ~85meV. This value is in good agreement with the difference in the work function between As-doped p- and n-type ZnO nanorods (96meV) measured with the same conditions. This value is smaller than the expected values estimated from the energy band diagram. However it is explained in terms of surface state and surface band bending.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.1038-1041
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• 2006

We report low operating voltage and long lifetime organic light-emitting diodes (OLEDs) with a vanadium oxide $(V_2O_5)-doped$ N,N'-di(1-naphthyl)- N,N'-diphenylbenzidine $({\alpha}-NPD)$ layer between indium tin oxide and ${\alpha}-NPD$. At a luminance of $1000\;cd/m^2$, $V_2O_5$ doped ${\alpha}-NPD$ device shows a operation voltage of 5.1V, while the device without $V_2O_5$ shows 5.8V. The $V_2O_5$ doped $({\alpha}-NPD)$ device also shows a longer lifetime and smaller operation voltage variation over time. It is suggested that the improved device performance can be attributed to the higher hole-injection efficiency and stability of the $V_2O_5$ doped $({\alpha}-NPD)$ layer.

• Transactions on Electrical and Electronic Materials
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• v.1 no.3
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• pp.6-9
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• 2000

Selectively excited photoluminescence(PL) spectroscopy has been carried out on the ~1540 nm $^{4}$I$_{13}$ 3/ to $^{4}$I/wub 15/2/ emissions of the multiple Er$^{3+}$ centers observed in Er-implante undoped and Mg-doped GAN at temperatures ranging from 6K to 295K. The temperature dependence of the Er$^{3+}$ PL spectra selectively excited by below -gap light demonstrates different quenching rates for the distinct Er$^{3+}$ centers, and indicates that the PL spectra with the most rapid thermal quenching rats do not contribute to the room temperature, above-p-pumped Er$^{3+}$ spectrum. In addition, selective PL spectroscopy has ben carried out on the Er$^{3+}$ emission in Er-implanted undoped and Mg-doped GaN at temperatures ranging 6K to 295K. The results indicate that the previously reported enhancement of the violet-pumped centers contribution to the low temperature above excited Er$^{3+}$ PL in Mg-doped GaN is also evident at room temperature.temperature.

• Journal of the Korean Vacuum Society
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• v.10 no.1
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• pp.67-71
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• 2001

Optical investigation on Zn-doped InGaN grown by MOCVD was performed by using the photoluminescence. Two different spectra related to Zn-acceptor-like centers occurred at room temperature, with broad emissions peaking at 2.81, and 2.60 eV, Specially, emissions interacted with phonon were observed at 2.81 eV where phonon energy was 92.5 meV From temperature dependent blue-band emissions of InGaN, we observe that the intensity in high energy region was quickly decreased more than that in low energy region with increased temperature, and the peak position at 2.81 eV was blue shift of about 18 meV, The blue-band emmissions would be originated from the transition related to the localized Zn complex centers.

• Carbon letters
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• v.16 no.1
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• pp.57-61
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• 2015

Carbon aerogel is a porous carbon material possessing high porosity and high specific surface area. Nitrogen doping reduced the specific surface area and micropores, but it furnished basic sites to improve the $CO_2$ selectivity. In this work, N-doped carbon aerogels were prepared with different ratios of resorcinol/melamine by using the sol-gel method. The morphological properties were characterized by scanning electron microscopy (SEM). Nitrogen content was studied by X-ray photoelectron spectroscopy (XPS) and the specific surface area and micropore volume were analyzed by $N_2$ adsorption-desorption isotherms at 77 K. The $CO_2$ adsorption capacity was investigated by $CO_2$ adsorption-desorption isotherms at 298 K and 1 bar. Melamine containing N-doped CAs showed a high nitrogen content (5.54 wt.%). The prepared N-doped CAs exhibited a high $CO_2$ capture capacity of 118.77 mg/g (at resorcinol/melamine = 1:0.3). Therefore, we confirmed that the $CO_2$ adsorption capacity was strongly affected by the nitrogen moieties.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.5
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• pp.419-424
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• 2009

ZnO films doped with different contents of indium ($0.1{\sim}10$ at.%) were deposited on Si (111) substrate by Pulsed Laser Deposition (PLD). The structural, electrical and optical properties of the films were investigated using XRD, AFM, Hall and PL measurement. Results showed that un-doped ZnO film had (002) plane as the c-axis orientated growth, whereas indium doped ZnO films exhibited the peak of (002) and the weak (101) plane. In addition, in the indium doped ZnO films, the electron concentration is ten times higher than that of un-doped ZnO film, while the resistivity is ten times lower than that of un-doped ZnO film. The indium doped ZnO films have UV emission about 380 nm and show a red shift with increasing contents of indium. The I-V curve of the fabricated diode show the typical diode characteristics and have the turn on voltage of about 2 V.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.29 no.3
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• pp.83-90
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• 2019

In this paper, Mg-doped AlN epilayers for power semiconductor devices are grown by mixed-source hydride vapor phase epitaxy. Magnesium is used as p-type dopant material in the grown AlN epilayer. The AlN epilayers on the GaN-templated sapphire substrate and GaN-templated-patterned sapphire substrate (PSS), respectively, as the base substrates for device application, were selectively grown. The surface and the crystal structures of the AlN epilayers were investigated by field emission scanning electron microscopy (FE-SEM) and high-resolution-X-ray diffraction (HR-XRD). From the X-ray photoelectron spectroscopy (XPS) and Raman spectra results, the p-type AlN epilayers grown by using the mixed-source HVPE method could be applied to power devices.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.15-16
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• 2008

We have grown N-doped ZnO thin films on sapphire substrate by employing dielectric barrier discharge in pulsed laser deposition (DBD-PLD). DBD guarantees an effective way for massive in-situ generation of N-plasma under the conventional PLD process condition. Low-temperature photoluminescence spectra of the N-doped ZnO film provided near band-edge emission after thermal annealing process. The emission peak was resolved by Gaussian fitting and showed a dominant acceptor-bound exciton peak ($A^0X$) that indicated the successful p-type doping of ZnO with N.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.6
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• pp.444-448
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• 2010

Based on first-principles calculations, we study the magnetic properties of Co, Ni, Fe, V, and Mn impurities in ZnO. The stabilities of the ferromagnetic state and the magnetic moment of each impurity largely depend on the amount of doped electron or hole. For lightly doped n-type ZnO, it is found that the doping of Ni ions is the most effective for inducing ferromagnetism, while Fe ions show the most stable ferromagnetic couplings for heavily doped n-type samples. The characteristics of the magnetic interactions of Co ions are similar with those of Fe ions, but Co ions require much larger amount of doped electron than Fe ions to show the ferromagnetic couplings. The ferromagnetic coupling between Mn and V ions is unstable in n-type conditions.

• Proceeding of EDISON Challenge
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• 2017.03a
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• pp.404-411
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• 2017

이 논문에서는 2차원 화합물 반도체인 Indium Selenide monolayer의 효과적인 도펀트 원소를 탐색해보았다. 총 4가지 종류의 원소를 도핑시켜 계산을 했다. In 자리에 Mg과 Sn을 도핑시켜 각각 p-type과 n-type으로 만들고 Se 자리에 As과 Br을 도핑시켜 각각 p-type과 n-type으로 만들었다. 변화한 성질을 알아보기 위해 전자 구조를 분석하고 band structure와 DOS를 살펴보았다. P-type 같은 경우, Mg doped InSe는 shallow defect level이 생겨 좋은 반도체로 쓰일 수 있지만 As을 도핑한 InSe는 deep defect states가 생겼다. VBM에서 약 0.67 eV만큼 떨어져있는데 이 수치는 실험값과 비슷한 값이다. N-type 경우에는 Sn doped InSe는 deep defect states가 생겼고, CBM 아래로 약 0.08eV만큼 defect가 생긴 것이 실험값과 비슷하다. Br doped InSe는 Sn doped InSe보다 안정적인 n형 반도체가 될 수 있다.