Vacuum field emission microelectronic devices based on silicon nanowhiskers

摘要

Vacuum field emission devices have become a promising candidate for emerging display technology due to their interesting properties compared to conventional thermionic emission devices that require high temperature and power to operate. Unlike thermionic emission, field emission devices can induce the electrons to emit at low temperature; sharp and thin emitters on the cathode are desired in order to increase the field emission. Many candidates from other research groups, such as Carbon Nanotubes (CNTs), SiC and ZnO, appear to have high field emission, but their complicated fabrication processes are the drawback. The silicon nanowhiskers produced by Geological & Nuclear Sciences (GNS) using Electron-Beam Rapid Thermal Annealing (EB-RTA) are an alternative material that is fast, inexpensive and uncomplicated to produce. They are based on the thermal desorption of silicon oxide, which forms silicon nanowhiskers on the silicon wafer in a short duration. Field emission diode structures on Silicon on Insulator (SOI) wafers were fabricated in order to investigate the field emission due to these GNS silicon nanowhiskers. An uncomplicated fabrication process using photolithography and etching process was developed. Electron beam lithography (EBL) was also used to create the different feature sizes directly onto the SOI wafer. The silicon nanowhiskers grown on these structures are as high as 35 nm with density distribution up to 30 µm⁻¹. The electrical characteristics of these devices are diode-like when the voltage range from -40 V to 40 V is applied. The best samples produced an emitted current as high as 2 mA, which is suitable for many applications, such as flat panel displays, x-ray sources and high frequency devices. However, in some cases, the diode structures failed to show the diode-like characteristics, perhaps as a result of bad contact connections or the emitters have been worn out after applying high voltage for some time. Device life time and stability were also considered and investigated via a number of electrical measurements for a period of time as long as one hour in this study. Even though these nanowhiskers have shown promising results, there are still many aspects to be considered to improve the experiments, such as the vacuum system and better contacts.