In the recent years, thin film solar cells (TFSCs) have emerged as a viable replacement for crystalline silicon solar cells and offer a variety of choices, particularly in terms of synthesis processes and substrates (rigid or flexible, metal or insulator). Among the thin-film absorber materials, SnS has great potential for the manufacturing of low-cost TFSCs due to its suitable optical and electrical properties, non-toxic nature, and earth abundancy. However, the efficiency of SnS-based solar cells is found to be in the range of 1 ~ 4 % and remains far below those of CdTe-, CIGS-, and CZTSSe-based TFSCs. Aside from the improvement in the physical properties of absorber layer, enormous efforts have been focused on the development of suitable buffer layer for SnS-based solar cells. Herein, we investigate the device performance of SnS-based TFSCs by introducing double buffer layers, in which CdS is applied as first buffer layer and ZnMgO films is employed as second buffer layer. The effect of the composition ratio (Mg/(Mg+Zn)) of RF sputtered ZnMgO films on the device performance is studied. The structural and optical properties of ZnMgO films with various Mg/(Mg+Zn) ratios are also analyzed systemically. The fabricated SnS-based TFSCs with device structure of SLG/Mo/SnS/CdS/ZnMgO/AZO/Al exhibit a highest cell efficiency of 1.84 % along with open-circuit voltage of 0.302 V, short-circuit current density of 13.55 mA cm−2, and fill factor of 0.45 with an optimum Mg/(Mg + Zn) ratio of 0.02.

We propose a speedy two-step deposit process to form an Au electrode on hole transport layer(HTL) without any damage using a general thermal evaporator in a perovskite solar cell(PSC). An Au electrode with a thickness of 70 nm was prepared with one-step and two-step processes using a general thermal evaporator with a 30 cm source-substrate distance and 6.0 × 10−6 torr vacuum. The one-step process deposits the Au film with the desirable thickness through a source power of 60 and 100 W at a time. The two-step process deposits a 7 nm-thick buffer layer with source power of 60, 70, and 80 W, and then deposits the remaining film thickness at higher source power of 80, 90, and 100W. The photovoltaic properties and microstructure of these PSC devices with a glass/FTO/TiO2/perovskite/ HTL/Au electrode were measured by a solar simulator and field emission scanning electron microscope. The one-step process showed a low depo-temperature of 88.5 oC with a long deposition time of 90 minutes at 60 W. It showed a high depo-temperature of 135.4 oC with a short deposition time of 8 minutes at 100 W. All the samples showed an ECE lower than 2.8% due to damage on the HTL. The two-step process offered an ECE higher than 6.25% without HTL damage through a deposition temperature lower than 88 oC and a short deposition time within 20 minutes in general. Therefore, the proposed two-step process is favorable to produce an Au electrode layer for the PSC device with a general thermal evaporator.

Recently, the use of an aluminum nitride(AlN) buffer layer has been actively studied for fabricating a high quality gallium nitride(GaN) template for high efficiency Light Emitting Diode(LED) production. We confirmed that AlN deposition after N2 plasma treatment of the substrate has a positive influence on GaN epitaxial growth. In this study, N2 plasma treatment was performed on a commercial patterned sapphire substrate by RF magnetron sputtering equipment. GaN was grown by metal organic chemical vapor deposition(MOCVD). The surface treated with N2 plasma was analyzed by x-ray photoelectron spectroscopy(XPS) to determine the binding energy. The XPS results indicated the surface was changed from Al2O3 to AlN and AlON, and we confirmed that the thickness of the pretreated layer was about 1 nm using high resolution transmission electron microscopy(HR-TEM). The AlN buffer layer deposited on the grown pretreated layer had lower crystallinity than the as-treated PSS. Therefore, the surface N2 plasma treatment on PSS resulted in a reduction in the crystallinity of the AlN buffer layer, which can improve the epitaxial growth quality of the GaN template.

We investigated the effect of ZnO buffer layer on the formation of ZnO thin film by ultrasonic assisted spray pyrolysis deposition. ZnO buffer layer was formed by wet solution method, which was repeated several times. Structural and optical properties of the ZnO thin films deposited on the ZnO buffer layers with various cycles and at various temperatures were investigated by field-emission scanning electron microscopy, X-ray diffraction, and photoluminescence spectrum analysis. The structural investigations showed that three-dimensional island shaped ZnO was formed on the bare Si substrate without buffer layers, while two-dimensional ZnO thin film was deposited on the ZnO buffer layers. In addition, structural and optical investigations showed that the crystalline quality of ZnO thin film was improved by introducing the buffer layers. This improvement was attributed to the modulation of the surface energy of the Si surface by the ZnO buffer layer, which finally resulted in a modification of the growth mode from three to two-dimensional.

In this study, we inserted a Zn buffer layer into a AZO/p-type a-si:H layer interface in order to lower the contact resistance of the interface. For the Zn layer, the deposition was conducted at 5 nm, 7 nm and 10 nm using the rf-magnetron sputtering method. The results were compared to that of the AZO film to discuss the possibility of the Zn layer being used as a transparent conductive oxide thin film for application in the silicon heterojunction solar cell. We used the rf-magnetron sputtering method to fabricate Al 2 wt.% of Al-doped ZnO (AZO) film as a transparent conductive oxide (TCO). We analyzed the electro-optical properties of the ZnO as well as the interface properties of the AZO/p-type a-Si:H layer. After inserting a buffer layer into the AZO/p-type a-Si:H layers to enhance the interface properties, we measured the contact resistance of the layers using a CTLM (circular transmission line model) pattern, the depth profile of the layers using AES (auger electron spectroscopy), and the changes in the properties of the AZO thin film through heat treatment. We investigated the effects of the interface properties of the AZO/p-type a-Si:H layer on the characteristics of silicon heterojunction solar cells and the way to improve the interface properties. When depositing AZO thin film on a-Si layer, oxygen atoms are diffused from the AZO thin film towards the a-Si layer. Thus, the characteristics of the solar cells deteriorate due to the created oxide film. While a diffusion of Zn occurs toward the a-Si in the case of AZO used as TCO, the diffusion of In occurs toward a-Si in the case of ITO used as TCO.

In this study, the effects of an annealed buffer layer with different thickness on heterojunction diodes based on the ZnO/ZnO/p-Si(111) systems were reported. The effects of an annealed buffer layer with different thickness on the structural, optical, and electrical properties of zinc oxide (ZnO) films on p-Si(111) were also studied. Before zinc oxide (ZnO) deposition, different thicknesses of ZnO buffer layer, 10 nm, 30 nm, 50 nm and 70 nm, were grown on p-Si(111) substrates using a radio-frequency sputtering system; samples were subsequently annealed at 700˚C for 10 minutes in N2 in a horizontal thermal furnace. Zinc oxide (ZnO) films with a width of 280nm were also deposited using a radio-frequency sputtering system on the annealed ZnO/p-Si (111) substrates at room temperature; samples were subsequently annealed at 700˚C for 30 minutes in N2. In this experiment, the structural and optical properties of ZnO thin films were studied by XRD (X-ray diffraction), and room temperature PL (photoluminescence) measurements, respectively. Current-voltage (I-V) characteristics were measured with a semiconductor parameter analyzer. The thermal tensile stress was found to decrease with increasing buffer layer thickness. Among the ZnO/ZnO/p-Si(111) diodes fabricated in this study, the sample that was formed with the condition of a 50 nm thick ZnO buffer layer showed a strong c-axis preferred orientation and I-V characteristics suitable for a heterojunction diode.

본 논문에서는 6,13-bis (triisopropylsily lethynyl)-pentacene (TIPS-pentacene) 유기 박막 트랜지스터에 니켈 버퍼층을 적층했을 때의 효과를 연구하였다. 니켈 (Nickel) / 은(Silver) 소스 드레인 전극은 은 (Silver) 전극이 단독으로 쓰일 때 보다 에너지 레벨차이를 줄여 캐리어의 주입이 더 잘되도록 도와주므로써 전기적 특성을 향상 시켜준다. 또한 유기 게이트 절연체의 추가로 TIPS-pentacene 은 규칙적 배열된 형태를 가지므로써 소자 성능의 향상을 가지고 온다. 제작한 유기박막트랜지스터 에서 0.01 cm2의 포화영역 이동도를 얻을 수 있었으며, 또한 드레인 전압을 50 V로 하고 게이트 전압을 20 V에서 -50 V 까지 인가하였을 때 2×104의 전멸 비를 얻을 수 있었다. 이러한 결과를 polyethylene terephthalate (PET) 기판을 이용한 유연한 OTFTs 에 적용시켜본 결과 유리기판위에 제작했을 때와 비슷한 성능을 얻음을 확인하였다.

In the microelectronics packaging industry, the adhesion strength between Cu and polyimide and the thermal stability are very important factors, as they influence the performance and reliability of the device. The three different buffer layers of Cr, 50%Cr-50%Ni, and Ni were adopted in a Cu/buffer layer/polyimide system and compared in terms of their adhesion strength and thermal stability at a temperature of 300˚C for 24hrs. A 90-degree peel test and XPS analysis revealed that both the peel strength and thermal stability decreased in the order of the Cr, 50%Cr-50%Ni and Ni buffer layer. The XPS analysis revealed that Cu can diffuse through the thin Ni buffer layer (200Å), resulting in a decrease in the adhesion strength when the Cu/buffer layer/polyimide multilayer is heat-treated at a temperature of 300˚C for 24hrs. In contrast, Cu did not diffuse through the Cr buffer layer under the same heat-treatment conditions.

TiAlN films were deposited on WC-5Co substrates with different buffer layers by D.C. magnetron sputtering. The films were evaluated by microstructural observations and measuring of preferred orientation, hardness value, and adhesion force. As a process variable, various buffer layers were used such as TiAlN single layer, TiAlN/TiAl, TiAlN/TiN and TiAlN/CrN. TiAlN coating layer showed columnar structures which grew up at a right angle to the substrates. The thickness of the TiAlN coating layer was about 1.8μm, which was formed for 200 minutes at 300˚. XRD analysis showed that the preferred orientation of TiAlN layer with TiN buffer layer was (111) and (200), and the specimens of TiAlN/TiAl, TiAlN/CrN, TiAlN single layer have preferred orientation of (111), respectively. TiAlN single layer and TiAlN/TiAl showed good adhesion properties, showing an over 80N adhesion force, while TiAlN/TiN film showed approximately 13N and the TiAlN/CrN was the worst case, in which the layer was destroyed because of high internal residual stress. The value of micro vickers hardness of the TiAlN single layer, TiAlN/TiAl and TiAlN/TiN layers were 2711, 2548 and 2461 Hv, respectively.

We have seen the effects of buffer layer in organic light-emitting diodes using poly(N-vinylcarbazole)(PVK). Polymer PVK buffer layer was made using static spin-casting method. Two device structures were made; one is ITO/TPD/Alq3/Al as a reference and the other is ITO/PVK/TPD/Alq3/Al to see the effects of buffer layer in organic light-emitting diodes. Current-voltage characteristics, luminance-voltage characteristics and luminous efficiency were measured with a variation of spin-casting speeds. We have obtained an improvement of luminous efficiency by a factor of two and half when the PVK buffer layer is used.

We have seen the effects of buffer layer in organic light-emitting diodes(OLEDs) using poly(N-vinylcarbazole)(PVK) depending on a concentration of PVK. Polymer PVK buffer layer was made using spin casting technique. Two device structures were fabricated; one is ITO/TPD/Alq3/Al as a reference, and the other is ITO/PVK/TPD/Alq3/Al to see the effects of buffer layer in organic light-emitting diodes. Current-voltage-luminance characteristics and an external quantum efficiency were measured with a variation of spin-casting rpm speeds and PVK concentration. We have obtained an improvement of external quantum efficiency by a factor of four when the PVK concentration is 0.1wt% is used. The improvement of efficiency is expected due to a function of hole-blocking of PVK in OLEDs.

Metal organic chemical vapor deposition (MOCVB)법을 사용하여 sapphire (0001) 기판 위에 GaN 환충층을 성장하고, 그 위에 GaN 에피층을 성장하였다. GaN 완충층은 550˚C에서 약 26 nm에서 130 nm까지 각각 다른 두께로 성장하였고, GaN 에피층은 1100˚C에서 약 4 μm의 두께로 성장하였다. GaN 완충층 성장 후 atomic force microscopy (AFM)으로 표면 형상을 측정하였다. GaN 완충층의 두께가 두꺼워질수록 GaN 에피층의 표면이 매끈해지는 것을 scanning electron microscopy (SEM)으로 관찰하였다. 이것으로 GaN 에피층의 표면은 완충층의 두께와 표면 거칠기와 관계가 있다는 것을 알 수 있었다. GaN 에피층의 결정학적 특성을 double crystal X-ray diffraction (DCXRD)와 Raman spectroscopy로 측정하였다. 성장된 GaN 에퍼층의 광학적 특성을 photoluminescence (PL)로 조사한 결과 두께가 두꺼운 완충층 위에 성장된 에퍼층의 결정성이 더 좋은 반면, 내부 잔류응력은 증가하는 결과를 보였다. 이러한 사실들로부터 완충층의 두께가 두꺼워짐에 따라 내부 자유에너지가 감소하여 에피층 성장시 측면성장을 도와 표면이 매끈해지고, 결정성이 좋아졌다.

Metal/ferroelectric/insulator/semiconductor(MFIS)-Field Effect Transistor을 위한 Pt/YMnO3/Y2O3/Si 구조를 제조하여 MFIS 구조의 특성에 미치는 Y2O3박막의 영향을 고찰하였다. PLD법을 이용하여 p=type Si(111) 기판 위에 증착시킨 Y2O3박막은 증착온도와 관계없이 (111)방향으로의 우선배향성을 갖고 결정화 되었다. 실리콘 위에 바로 MOCVD법에 의해 강유전체 YMnO3박막을 증착시킨 경우 실리콘과의 계면에서 Mn이 부족한 층이 형성되지만 Y2O3가 실리콘과 YMnO3사이에 삽입된 경우는 Y2O3바로 위에서부터 화학양론비에 일치하는 양질의 YMnO3박막을 얻을 수 있었다. 850˚C, 100mtorr의 진공분위기에서 열처리한 YMnO3박막은 Y2O3가 삽입된 경우 memory window 값이 Y2O3가 삽입되지 않은 경우보다 더 큰 값을 보였으며 5V에서 1.3V의 값을 보였다.

플라즈마 화학증착 (PECVD) 장비를 이용하여 SnO2 투명전도막이 피막된 유리기판 위에 p-SiC/i-Si/n-Si 이종접합 태양전지를 제작하였다. p-SiC 층의 증착중에 기체조성 x=CH4/ (SiH4+CH4)의 변화에 대한 태양전지의 광기전 특성을 관찰하였다. 기체조성(x)이 0~0.4의 범위에서 p-SiC 창층의 광학적 밴드갭의 증가로 인하여 태양전지의 효율은 증가하였으나, 그 이상의 기체조성에서는 p-SiC/i-Si 계면에서의 조성불일치가 증가하여 태양전지의 효율이 감소하였다. 이러한 계면문제는 p-SiC 층과 i-Si 계면에서의 조성불일치가 증가하여 태양전지의 효율이 감소하였다. 이러한 계면문제는 p-SiC 층과 I-Si 층 사이에 I-SiC 완충층을 삽입함으로써 크게 감소하였다. 그 결과 유효면적이 1cm2인 glass/SnO2/p-SiC/i-SiC/i-Si/n-Si/Ag 구조의 박막 태양전지는 100mW/cm2 조도 하에서 8.6%의 효율을 나타내었다. (Voc=0.85V, Jsc=16.42mA/cm2, FF=0.615)

AIN과 저온 GaN 완충충율 이용하여 Si 기판 위의 후막 GaN의 성장특성을 조샤하였다. Si과 GaN의 격자부정합도와 열팽창계수의 차이를 줄이기 위해 AIN과 저온 GaN를 완충충으로 사용하였다. AIN은 RF sputter를 이용하여 중착온도와 증착시간 및 RF power에 따른 표면 거칠기를 AFM으로 조사하여 최척조건을 확립하여 사용하였다. 또한 저온에서 GaN를 성장시켜 이를 완충충으로 이용하여 후막 GaN의 성장시 미치는 영향을 살펴보았다. 성장온도와 V/III 비율이 후막 성장시 표면특성과 결정성 및 성장속도에 미치는 영향을 조사하였다. 후막 GaN의 표연특성 및 막의 두께는 SEM과 α-step을 이용하여 측정하였으며 결정성은 X-ray Diffractometer를 이용하여 조사하였다.

In this paper, the wind tunnel test was carried to investigate the behavior of buffer layer in turbulent boundary layer with variation of surface temperature and roughness. The results were as follows; 1. The velocity in turbulent boundary layer was increased when the roughness height within viscous sublayer thickness was increased. 2. When the surface temperature was increased, the density of air was decreased and the velocity in turbulent boundary layer was increased. Thus, the thickness of turbulent boundary layer was decreased. 3. When the roughness height and surface temperature was increased simultaneously, the thickness of turbulent boundary layer was decreased. 4. The decrement of the thickness of turbulent boundary layer was more effected by the increment of the roughness height rather than the increment of surface temperature. 5. In this study, it was found that the condition of the highest velocity n turbulent boundary layer was the temperature 333K and roughness #100.