Hyejeong Jeong

Structural and Electrical Properties of Polysilicon Films Prepared by AIC Process for a Polycrystalline Silicon Solar Cell Seed Layer

Polycrystalline silicon (pc-Si) films are produced by aluminum-induced crystallization (AIC) process for a polycrystalline silicon solar cell seed layer, and the structural and electrical properties of the films are analyzed. The used structure is glass/Al/ Al2O3/a-Si, and the thickness of Al2O3 layer was varied from 2 nm to 20 nm to investigate the influence of the Al2O3 layer thickness on the formation of the polycrystalline silicon. The annealing temperature and annealing time were fixed to 400∘C and 5 hours, respectively, for the AIC process conditions. As a result, it is observed that the average grain size of the pc-Si films is rapidly smaller with increasing the thickness of Al2O3 layer, whereas the film quality, as defects and Hall mobility, was gradually degraded with only small difference. We obtained the maximum average grain size of 15 μm for the pc-Si film with the thickness of Al2O3 layer of 4 nm. The best resistivity and the Hall mobility was 6.1×10−2 Ω⋅cm and 90.91 cm2/Vs, respectively, in the case of 8 nm thick Al oxide layer.

Fabrication of Micro-sized Al/Cu Clad by Repeated Hydrostatic Extrusion and Its Mechanical Properties

Al/Cu clads were fabricated by hydrostatic extrusion at 523 K, and their microstructure and mechanical properties were evaluated. The cell size of the Al/Cu clads decreases from 12 mm to 600 µm after three passes of extrusion. Intermetallic compounds (IMCs) appeared at the interface of Al/Cu clad during annealing at 683 K, and their sizes increased as a function of the annealing process. X-ray microanalysis and scanning electron microscope studies showed that the intermetallic species were CuAl2, CuAl, and Cu3Al2, and the thickness of the IMC layers increased at different rates depending on the annealing time. The formation and growth of IMCs resulted in an increase of yield strength and a decrease in elongation of the clads under tensile testing.

Investigation of aluminum-induced crystallization of amorphous silicon and crystal properties of the silicon film for polycrystalline silicon solar cell fabrication

Polycrystalline silicon (pc-Si) films are fabricated and characterized for application to pc-Si thin film solar cells as a seed layer. The amorphous silicon films are crystallized by the aluminum-induced layer exchange (ALILE) process with a structure of glass/Al//a-Si using various thicknesses of layers. In order to investigate the effects of the oxide layer on the crystallization of the amorphous silicon films, such as the crystalline film detects and the crystal grain size, the layer thickness arc varied from native oxide to 50 nm. As the results, the defects of the poly crystalline films are increased with the increase of layer thickness, whereas the grain size and crystallinity are decreased. In this experiments, obtained the average pc-Si sub-grain size was about at relatively thin layer thickness ( 16 nm). The preferential orientation of pc-Si sub-grain was .

Properties of poly silicon films deposited on silicon seed-layers prepared by AIC process

A polycrystalline silicon (pc-Si) film is produced by low-temperature LPCVD process on a poly silicon seed layer. The properties of such film are characterized and compared with the films on a glass substrate and a silicon wafer. The poly crystalline silicon seed layers are fabricated by aluminum-induced crystallization (AIC) process with a glass/Al/Al2O3/a-Si structure, in which the Al layer was deposited on the glass substrate by a DC magnetron sputter, and a-Si film by PECVD method, respectively. After the AIC process with 400°C for 150min, the poly silicon film has the average grain size of about 10μm. The poly silicon seed layer is thickened (i.e. the poly silicon film is deposited on the seed layer) by LPCVD process with 600°C for 60min. As results, it is observed that the quality of the poly silicon film on the seed layer is better than that on the glass and worse than that on the silicon wafer. But the deposited poly silicon absorber layer could not reflect the property of the poly silicon seed layer, due to the relatively low temperature process.

Tribological and Electrical Properties of Diamond-Like Carbon Films Deposited by Filtered Vacuum Arc Method for Medical Guidewire Application

A good medical guidewires are used to introduce stents, catheters, and other medical devices inside the human body. In this study, diamond-like carbon (DLC) film was proposed to solve the poor adhesion problem of guidewire and to improve the tribological performance of guidewire. DLC films were fabricated on Si substrate by using FVA (Filtered Vacuum Arc) method. In this work, the tribological, structural, and electrical properties of the fabricated DLC films with various arc currents were experimentally investigated. All DLC films showed smooth and uniform surface with increasing applied arc current. The rms surface roughness was increased and the value of contact angle on the film surface was decreased with increasing arc current. The hardness and elastic modulus of DLC films were improved, and the resistivity value of DLC films were decreased with increasing arc current. These results are associated with ion bombardment effects by the applied arc current and bias voltage.

Characterization of polycrystalline silicon films produced by aluminum-induced layer exchange for the various thicknesses of an aluminum oxide layer

We characterized polycrystalline silicon films produced by aluminum-induced layer exchange (ALILE) for the various thicknesses of an aluminum oxide layer. The pc-Si film is fabricated by the ALILE process with a structure of glass/Al/Al<inf>2</inf>O<inf>3</inf>/a-Si for application to a seed layer of polycrystalline silicon (pc-Si) solar cells using dc and RF sputtering, and PECVD methods, respectively. For investigation of the effects of oxide film thickness on the crystallinity in the ALILE process, the thickness of Al<inf>2</inf>O<inf>3</inf> was varied from 4 to 50 nm including native oxidation in the ambient atmosphere. For characterization OM, SEM, Raman spectroscopy analyses are carried out. As results, the crystallinity was exponentially decayed with increase of Al<inf>2</inf>O<inf>3</inf> thickness. Also, the grain size is decreased with increase of Al<inf>2</inf>O<inf>3</inf> layer thickness. The maximum pc-Si grain size of about 60 µm is obtained at the relatively thin oxide layer. The preferential crystal orientation was (111) and more dominant for the thinner Al<inf>2</inf>O<inf>3</inf> layers. In this work the effects of Al<inf>2</inf>O<inf>3</inf> film thickness on the crystallization properties of a-Si by ALILE process are closely demonstrated such as grain size, preferential crystal orientation, and crystallinity.