Capacitance-voltage analysis of electrical properties for WSe2 field effect transistors with high-k encapsulation layer.

Doping effects in devices based on two-dimensional (2D) materials have been widely studied. However, detailed analysis and the mechanism of the doping effect caused by encapsulation layers has not been sufficiently explored. In this work, we present experimental studies on the n-doping effect in WSe2 field effect transistors (FETs) with a high-k encapsulation layer (Al2O3) grown by atomic layer deposition. In addition, we demonstrate the mechanism and origin of the doping effect. After encapsulation of the Al2O3 layer, the threshold voltage of the WSe2 FET negatively shifted with the increase of the on-current. The capacitance-voltage measurements of the metal insulator semiconductor (MIS) structure proved the presence of the positive fixed charges within the Al2O3 layer. The flat-band voltage of the MIS structure of Au/Al2O3/SiO2/Si was shifted toward the negative direction on account of the positive fixed charges in the Al2O3 layer. Our results clearly revealed that the fixed charges in the Al2O3 encapsulation layer modulated the Fermi energy level via the field effect. Moreover, these results possibly provide fundamental ideas and guidelines to design 2D materials FETs with high-performance and reliability.

Video-assisted thoracoscopic surgery under O-arm navigation system guidance for the treatment of thoracic disk herniations: surgical techniques and early clinical results.

This study describes the surgical technique and clinical results of video-assisted thoracoscopic surgery (VATS) assisted by an O-arm-based navigation system, used for the treatment of thoracic disk herniation (TDH). The trend toward the use of minimally invasive procedures with endoscopic visualization of the thoracic cavity in thoracic spine surgery has evolved. It is difficult to develop a new set of visuomotor skills unique to endoscopic procedures and understand the three-dimensional (3D) anatomy while performing a two-dimensional (2D) imaging procedure. Adding image guidance would have a positive impact on these procedures, making them safer and more precise. We report the results of 10 patients who underwent diskectomy for TDH using VATS assisted by an O-arm-based navigation system and describe the surgical technique. The average duration of the symptoms was 2.8 years; average operation time, 326.9 minutes; and average additional time required for the image guidance surgery using the O-arm-based navigation, ∼ 29.4 minutes. No complications occurred during the surgical procedure or the immediate postoperative period. The advantages of using navigational assistance during the surgical procedure include better visualization of the operative field, more accurate surgical planning, and optimization of the surgical approach involving the establishment of the correct drilling trajectory and safe decompression of the spinal cord, as well as the possibility of intraoperative control of bone resection.