The mechanism of field emission for diamond films studied by scanning tunneling microscopy

Journal of Nanomaterials

Wang

et al. 2014

The atomic-scale microstructure and electron emission properties of boron and sulfur (denoted as B-S) codoped diamond films grown on high-temperature and high-pressure (HTHP) diamond and Si substrates were investigated using atom force microscopy (AFM), scanning tunneling microscopy (STM), secondary ion mass spectroscopy (SIMS), and current imaging tunneling spectroscopy (CITS) measurement techniques. The films grown on Si consisted of large grains with secondary nucleation, whereas those on HTHP diamond are composed of well-developed polycrystalline facets with an average size of 10–50 nm. SIMS analyses confirmed that sulfur was successfully introduced into diamond films, and a small amount of boron facilitated sulfur incorporation into diamond. Large tunneling currents were observed at some grain boundaries, and the emission character was better at the grain boundaries than that at the center of the crystal. The films grown on HTHP diamond substrates were much more perfect with higher quality than the films deposited on Si substrates. The localI-Vcharacteristics for films deposited on Si or HTHP diamond substrates indicate n-type conduction.

Section: Methodsmentioning

confidence: 99%

Study on the Microstructure and Electrical Properties of Boron and Sulfur Codoped Diamond Films Deposited Using Chemical Vapor Deposition

Journal of Nanomaterials

Wang

et al. 2014

“…In this letter, we report on the microstructures and electrical properties of CVD diamond films that were investigated by atomic force microscopy (AFM) and scanning tunneling microscopy (STM) [8,9]. Current imaging tunneling spectroscopy (CITS) [10] was used to compare the structures and electrical properties of the doped diamond films on Si and HTHP diamond substrates.…”

Section: Methodsmentioning

confidence: 99%

The Study on the Microstructure and Electrical Property of Boron and Sulfur Co-Doped Diamond Films by Chemical Vapor Deposition

Wang

2012

AMM

The atomic-scale microstructure and electron emission properties of boron and sulfur (denoted as B-S) codoped diamond films grown on high-temperature and high-pressure (HTHP) diamond and Si substrates were investigated using atom force microscopy (AFM), scanning tunneling microscopy (STM) and current imaging tunneling spectroscopy (CITS) measurement techniques. The films grown on Si consisted of large grains with secondary nucleation, whereas those on HTHP diamond are composed of well-developed polycrystalline facets with an average size of 10–50 nm. Large tunneling currents were observed at some grain boundaries, and the emission character is better at the grain boundaries than at the center of the crystal. The codoped films grown on HTHP diamond have an almost uniform electron emission efficiency at grain boundaries or crystalline facets, which indicates that the doped atoms are uniformly distributed in the films. The local I-V characteristics for films deposited on Si or HTHP diamond substrates indicate n-type conduction.

The growth process and field emission characteristics of globe-like polycrystalline diamond films

2010 8th International Vacuum Electron Sources Conference and Nanocarbon

et al. 2010

Diamond film as cold cathode material has unique properties, especially high bonding force with substrate and resistance to ion-bombardment. We had reported that the stable tum-on field of globe-like microcrystalline diamond aggregates films grown on titanium coated ceramic substrates by microwave plasma chemical vapor deposition (MPCVD) was 1. 27V/Ilm and the current density reached 7.2mA/cm 2 at the electric fields of 2. 55V/llm [1].In this paper, the growth process and field-emission(FE) characteristics of globe-like polycrystalline diamond films grown on titanium coated Si substrates were studied.The diamond films were grown on Si substrates by MPCVD using Ti as buffer deposited by magnetron sputtering method. The source gas was a mixture of H 2 and CH 4 with flow rates of 100 and 12 sccm. During the deposition, total pressure of 11 KPa and microwave power of 1600W was kept. The deposition times were 2min, 30min, 1h and 2h, respectively.Scanning electron microscopy (SEM) and Raman scattering spectroscopy were utilized to characterize the morphology and microstructure of samples. The macroscopic FE current-voltage(I-V) curve was measured by diode structure in a vacuum of below 5xlO-4 Pa. Microscopic characteristics and local FE measurements were studied by scanning tunneling microscope (STM) in a vacuum of below 1O-8 Pa. The STM image of the surface was taken under the constant-current mode. The tip was then withdrawn from the surface to a fixed point by reducing the set point current and switching the sample bias voltage from -1.5 to + 1. 5V. The tunneling current as a function of bias voltage was able to depict the emission efficiency [2] .From the results of SEM photographs (Fig. 1 ) and Raman spectra of the samples, the growth process of globe-like polycrystalline diamond film was that: initially an amorphous carbon layer was formed on substrate (Fig. 1a), then diamond nucleated and grew on the amorphous carbon layer, accompanied by secondary nucleation (Fig. 1 b and Fig. 1 c), finally formed the globe-like polycrystalline diamond film (Fig.1d). The tum-on field of the film deposited at 2h was 0.92V/llm and the current density was 0. 62mA/cm 2 at the electric field of 2V 111m. Fig.2a showed the STM image of the diamond film deposited at 2h. Fig.2b indicated the local FE measurement corresponding to Fig.2a. The currents of points 1 and 8were near zero. Points 4 and 6 were near the boundary of diamond particle and points 3 and point 5 were at the top of diamond particle. The results revealed that the FE efficiency at the diamond particle top was larger than other sites.