Sukwon Lee

Enhanced Device Performance of Germanium Nanowire Junctionless (GeNW-JL) MOSFETs by Germanide Contact Formation with Ar Plasma Treatment

In this study, germanium nanowire junctionless (GeNW-JL) metal-oxide-semiconductor-field-effect-transistors (MOSFETs) exhibited enhanced electrical performance with low source/drain (S/D) contact resistance under the influence of Ar plasma treatment on the contact regions. We found that the transformation of the surface oxide states by Ar plasma treatment affected the S/D contact resistance. With Ar plasma treatment, the germanium dioxide on the GeNW surface was effectively removed and increased oxygen vacancies were formed in the suboxide on the GeNW, whose germanium-enrichment surface was obtained to form a germanide contact at low temperature. After a rapid thermal annealing process, Ni-germanide contacts were formed on the Ar-plasma-treated GeNW surface. Ni-germanide contact resistance was improved by more than an order of magnitude compared to that of the other devices without Ni-germanide contact. Moreover, the peak field effect mobility value of the GeNW-JL MOSFETs was dramatically improved from 15 cm(2)/(V s) to 550 cm(2)/(V s), and the Ion/off ratio was enhanced from 1 × 10 to 3 × 10(3) due to Ar plasma treatment. The Ar plasma treatment process is essential for forming uniform Ni-germanide-contacts with reduced time and low temperature. It is also crucial for increasing mass productivity and lowering the thermal budget without sacrificing the performance of GeNW-JL MOSFETs.

The Mechanism of Schottky Barrier Modulation of Tantalum Nitride/Ge Contacts

In this letter, we discuss the mechanism of Schottky barrier height (SBH) modulation of the TaN/Ge contact by varying the nitrogen concentration in the TaN. The Fermi level, which is strongly pinned near the valence band edge of Ge, moves to the conduction band edge of Ge with higher nitrogen concentration in the reactive sputtered TaN. This SBH modulation is attributed to the presence of an electric dipole induced by Ge-N bonds at the interface of the TaN/Ge contact. This SBH modulation due to the semiconductor-nitrogen bonds at the interface is not specific to TaN/Ge, but rather is a general feature in various transition-metal nitride systems on various semiconductors.

Trajectory-free reactive stepping of humanoid robots using momentum control

Momentum control approaches have been successfully applied to balance controllers for humanoid robots due to their integrated controllability of ground reaction force and the center of pressure. In this paper, we introduce a trajectory-free reactive stepping controller using momentum control. The controller is characterized by moving passively in the direction of external pushes without attempting to follow some prescribed trajectory, thereby achieving a natural reactive stepping behavior adaptive to various perturbations. Constructed on top of momentum control, our stepping controller is realized straightforwardly by setting a set of suitable inputs such as the desired momentum rate change and the target swing foot position to the momentum controller for each phase of stepping. We demonstrate the effectiveness of our approach through various simulation experiments on a humanoid robot model.

An Efficient Motion Graph Searching Algorithm for Augmented Reality Characters

Realistic motion of virtual characters is a crucial factor for the reality and immersiveness of an AR application. Motion graph-based approach allows for generating infinitely many types of motions and may create remarkably realistic human motion from a limited set of motion data. In this paper, we present a method to efficiently search the motion graph using A* search algorithm in an AR environment. Specifically, we introduce three types of heuristic functions: the distance, previewed distance, and directional heuristic functions. The proposed heuristic functions reduce compute time significantly while not sacrificing the quality of motion. We demonstrate the effectiveness of our method by implementing an interactive AR application.

Multifinger interaction between remote users in avatar-mediated telepresence

In avatar‐mediated telepresence, remote users find it difficult to engage and maintain contact, such as a handshake, with each other without a haptic device. We address the problem of adjusting an avatars pose to promote multifinger contact interaction between remote users. To this end, we first construct a contact point database for nine types of contact interactions between hands through contact experiments with human subjects. We then develop an optimization‐based framework to compute the avatars pose that realizes the desired contact learned from the experiment while maintaining the naturalness of the hand pose. We show that our method improves the quality of hand interaction for the predefined set of social interactions.

Responsive Motion Generation

In this chapter, we discuss the generation of natural behaviors of humanoids (virtual human characters in particular) responsive to the physical interaction with the user such as push and pull. These physical interactions play an important role for increasing the level of immersion of the user and lay foundations for more advanced level of interactions. One of the key components for physical interaction is the generation of suitable balancing behaviors of humanoids against user inputs. We review three major approaches for humanoid balancing, namely the ZMP-based methods, data-driven methods, and momentum-based methods. For each method, we discuss its basic ideas and principles, exemplar work, as well as important future research directions.

Trajectory-free reactive stepping of physics-based character using momentum control

We introduce a trajectory-free reactive stepping controller using momentum control. The controller is characterized by moving passively in the direction of external pushes without attempting to follow some prescribed trajectory, thereby achieving a natural reactive stepping behavior adaptive to various perturbations.

Constructing an avatar-based telepresence system using commodity hardware

This paper introduces a framework for an augmented reality (AR) telepresence system that utilizes virtual avatars as a medium for the interaction between remote users. Our system is built with only commodity hardware devices for sensor and display: the Kinect for Windows v2 for capturing a users motion and detecting an object, and the Oculus Rift DK2 with the Ovrvision for displaying camera images augmented with a virtual avatar. Each site is equipped with the same hardware setting and each user sees a virtual avatar representing the remote user augmented in the respective site. We demonstrate our system by showing two experiments; the handshaking between a user and a virtual avatar, and generation of an avatars sitting motion on a chair different from that in a remote site.