SEMINÁR ÚI SAV

ktorý sa bude konať v utorok 28. 2. 2023 o 10.30 hod. v zasadačke ÚI SAV č. 102.

Program:
1. Triboelectric Nanogenerator with Aligned Carbon Nanotube
Ruei–Chi Hsu, Ph.D. Department of Power Mechanical Engineering, National Tsing Hua University, Hsinchu, TAIWAN

2. Field Emission characteristics of laser selective growth CNFB–CNT
Yi–Hung Chen (Ph.D. Candidate) Department of Power Mechanical Engineering, National Tsing Hua University, Hsinchu, TAIWAN

1. A triboelectric nanogenerator (TENG) is one of the most promising approaches for self–powered energy conversion devices, which could transfer mechanical energy into electrical energy. Besides, this well–known technique has been brought to attention concerning its high–powered output, low cost, sustainability, and wearable application. This wearable device could be attached to the human body to generate energy by walking, running, or any friction movement.

Every material has either triboelectric positive or triboelectric negative characteristics. When the difference between the friction affinity of two materials is enormous, the produced electrical charges will enhance the output performance. On the other hand, another improvement in output performance TENG can be attributed to the triboelectric layer’s surface contact area and the surface charge density.

We proposed to use thermal chemical vapor deposition (CVD) to grow a vertically aligned carbon nanotube (CNT) as a triboelectric layer. CNT has the advantage of good conductivity, flexibility, and mechanical property, which can be used as field emission devices, actuators, and sensors. One main reason that affects the growth of CNT is the buffer layer deposited on the silicon wafer. It is found that the Al2O3 buffer layer has a significant impact on the catalyst particle with a small average size, a large density, and a uniform size distribution. Hence, the annealing treatment on the Al2O3 buffer layer was investigated and will be discussed further.

Keywords：TENG, CNT, Al2O3 buffer layer, Thermal CVD

2. Field emission is one of the electron–emitting methods that recently have been applied to the scientific or industrial fields, such as the electron microscope, microwave amplifier, display, cathode ray tube, plasma generator, and source of x–ray. When an electrical field is applied to the material, it creates the tunneling effect or Schottky effect on the electrons at the surface, increasing the possibility of these electrons conquering the energy barrier with energy lower than required and emitting to the environment. Since the field emission effect is highly related to the electrical field, proper emitter distribution guarantees better emission efficiency and reduces the screening effect. As a result, many previous studies are dedicated to improving the field emission properties by adjusting the density and distribution of the emitters or changing the material with lower work functions.

This study uses the carbon nanoflake ball (CNFB) as the emitter’s material. CNFB is a novel carbon–based composite material discovered by Ping–Huan Tsai, 2018. It is a sphere–like material constructed with multi–direction carbon composite flakes. Each flake has a diamond core covered by a few graphene layers. During the field emission process, the diamond core provides a robust construction with good heat conduction, while the graphene layer transports the electrons with lower resistance. Another unique characteristic of the CNFB is the synthesis mechanism. When synthesizing CNFBs with microwave plasma chemical vapor deposition (MPCVD), the nucleation sites of the CNFB are highly possible to be generated at the surface’s defect.

With the properties of the CNFB, this study proposed a method of using the laser to create designed defect patterns on the silicon surface to study the selective growth of CNFBs, and the relationship between the laser and the deposition of CNFB is discussed. To further improve the field emission characteristics of the CNFB, A layer of carbon nanotubes (CNT) is deposited on the patterned CNFBs. The result of the field emission shows a promising improvement in the turn–on field voltage and the threshold voltage with the designed pattern.

Keywords: Field emission, Carbon nanoflake ball, Laser, MPCVD, CNT

Tešíme sa na stretnutie s Vami pri šálke kávy alebo čaju.
Ing. Mgr. Robert Andok, PhD.
riaditeľ