Study of amorphous layer on CVD diamond surface induced by Ga ion implantation in focused ion beam processing

As a third-generation semiconductor material, chemical vapor deposition (CVD) diamond single crystals find crucial applications in electronic devices. While focused ion beam (FIB) milling which is a commonly employed method for processing micro/nano electronic devices, it inevitably results in the implantation of ion source materials and the formation of tens of nanometers of damaged layer, which is typically excessively thick for modern micro/nano electron devices. This study systematically explores the damaged layer induced by Ga ions during FIB diamond processing. The research revealed that damaged layer on the diamond surface measures 43 nm under 30 kV. The structure and electronic properties of the damaged layer were analyzed using high spatial resolution transmission electron microscopy (TEM) and high energy resolution electron energy loss spectroscopy (EELS) techniques. The findings indicate that the damaged layer consists of a double -layer structure, identified as an a -C I layer mainly composed of sp 2 hybridized carbon atoms and an a -C II layer primarily composed of sp 3 hybridized carbon atoms. Through the integration of results from energy -dispersive X-ray spectroscopy (EDS), EELS, and stopping and range of ions in matter (SRIM) simulations, it was determined that the a -C I layer is predominantly caused by the direct implantation of Ga ions, whereas the a -C II layer is primarily influenced by carbon recoil atoms. Remarkably, a 4.0 eV bandgap was deduced from the EELS spectrum of the a -C II layer. This semiconducting amorphous carbon layer (a -C II) and the diamond substrate together form an all-carbon heterostructure, suggesting potential applications in field-effect transistors.