Tae-Gon Kim

The fabrication of metal silicide nanodot arrays using localized ion implantation

We propose a process for fabricating nanodot arrays with a pitch size of less than 25xa0nm. The process consists of localized ion implantation in a metal thin film on a Si wafer using a focused ion beam (FIB), followed by chemical etching. This process utilizes the etching resistivity changes of the ion beam irradiated region that result from metal silicide formation by ion implantation. To control the nanodot diameter, a threshold ion dose model is proposed using the Gaussian distribution of the ion beam intensities. The process is verified by fabricating nanodots with various diameters. The mechanism of etching resistivity is investigated via x-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES).

Mechanical Cutting Process Trends for Difficult-to-Cut Materials - A Review -

Lightweight parts are necessary to improve fuel efficiency and reduce environmental impacts in transportation industry. As a result, there has been a shift away from using conventional metals toward using lighter materials with superior mechanical strength. These new materials typically include titanium alloys, nickel alloys, carbon fiber reinforced plastics (CFRPs), and CFRP-metal stacks, which are classified as advanced materials. However, due to the unique properties of these materials (e.g., high strength, low thermal conductivity, carbon fiber-induced hardness, etc.), the cutting process can be difficult. As a result, various manufacturing issues can occur during the cutting process, such as high tool wear, surface quality deterioration, delamination of the CFRP layer, fiber pull-out, and thermal deformation. In this paper, difficult-to-cut advanced materials were reviewed with regard to the influence of the physical properties of the materials and various defect issues that can occur during the mechanical cutting process. In addition, various approaches to improve the cutting process are introduced, including protecting tools with coatings, altering tool features, using high pressure or cryogenic cooling, extending tool life via ultrasonic vibration machining, and improving product quality and machinability.

CFRP Drilling Experiments: Investigation on Defect Behaviors and Material Interface Detection for Minimizing Delamination

CFRP (Carbon Fiber Reinforced Plastic) and CFRP-metal stacks have recently been widely used in the aerospace and automobile industries. When CFRP is machined by a brittle fracture mechanism, defect generation behaviors are different from those associated with metal cutting. The machining quality is strongly dependent on the properties of CFRP materials. Therefore, process control for CFRP machining is necessary to minimize the defects of differently manufactured CFRPs. In this study, defects in drilling of CFRP substrates with a variety of fiber directions and resin types are compared with respect to thrust force. An experimental study on material interface detection is carried out to investigate its benefits in process control.