Field-Induced Crystalline-to-Amorphous Phase Transformation on the Si Nano-Apex and the Achieving of Highly Reliable Si Nano-Cathodes.

Yifeng Huang,Ningsheng Xu,Juncong She,Weiliang Wang,Chaolun Liang,Shaozhi Deng,Zexiang Deng

doi:10.1038/srep10631

Abstract

Nano-scale vacuum channel transistors possess merits of higher cutoff frequency and greater gain power as compared with the conventional solid-state transistors. The improvement in cathode reliability is one of the major challenges to obtain high performance vacuum channel transistors. We report the experimental findings and the physical insight into the field induced crystalline-to-amorphous phase transformation on the surface of the Si nano-cathode. The crystalline Si tip apex deformed to amorphous structure at a low macroscopic field (0.6~1.65 V/nm) with an ultra-low emission current (1~10 pA). First-principle calculation suggests that the strong electrostatic force exerting on the electrons in the surface lattices would take the account for the field-induced atomic migration that result in an amorphization. The arsenic-dopant in the Si surface lattice would increase the inner stress as well as the electron density, leading to a lower amorphization field. Highly reliable Si nano-cathodes were obtained by employing diamond like carbon coating to enhance the electron emission and thus decrease the surface charge accumulation. The findings are crucial for developing highly reliable Si-based nano-scale vacuum channel transistors and have the significance for future Si nano-electronic devices with narrow separation.

Highlights

Nano-scale vacuum channel transistors, relying on the ballistic electron transport in vacuum, are favorable for a variety of potential applications, i.e., sensors, ultra-high speed transistors and THz amplifiers[1,2,3,4,5]
The physical mechanism was proposed by considering the strong electrostatic force on the electrons that accumulated in the high dopant density surface, which is based on the First-Principle calculations with density functional theory (DFT)
Both the transmission electron microscope (TEM) and selected area electron diffraction (SAED) results indicate that the crystalline-to-amorphous phase transformation happened locally at the Si tip surface

Summary

Introduction

Nano-scale vacuum channel transistors, relying on the ballistic electron transport in vacuum, are favorable for a variety of potential applications, i.e., sensors, ultra-high speed transistors and THz amplifiers[1,2,3,4,5]. Intensive studies have been performed on the fabrication and characterization of the vacuum channel transistors, which were realized by employing nano-scale field electron emission cathodes[2,3,4,5,6,7,8,9]. There is little understanding on the dramatic changes in the lattice of a semiconductor cathode subjected to an ultra-high electric field, especially insofar as the intriguing observation of their crystalline-to-amorphous phase transformation. Very less attention has been paid on the atomic-scale material-related mechanisms to the reliability of the vacuum nano-channel, the cathode reliability, under a high electric field. The findings are crucial for developing highly reliable Si-based nano-scale vacuum channel transistors and may have the significance for future Si nano-electronic device with narrow separation

Methods

Results

Conclusion