Jing Sheng Ma

Selective nucleation and growth of diamond particles by plasma‐assisted chemical vapor deposition

Diamond particles have been selectively synthesized on a SiO2 dot‐patterned Si substrate using plasma‐assisted chemical vapor deposition (plasma CVD). Nucleation densities on both Si and SiO2 have been increased, first by pretreatment using abrasive powders; then, to eliminate the pretreatment effect from almost all of the substrate and to retain the effect only at designed sites, an Ar beam is used to obliquely irradiate the pretreated substrate. After deposition using plasma CVD, diamond particles have selectively formed on one edge of the SiO2 dots according to the pattern and have grown large to adjoin with adjacent particles. Polycrystals with equal grain sizes have been synthesized.

Nucleation control and selective growth of diamond particles formed with plasma CVD

Abstract To obtain polycrystals with large and uniform grain size, diamond particles have been selectively formed on a SiO 2 dot-patterned Si substrate using plasma-assisted CVD. After pretreatment by abrasive powders to increase diamond nucleation densities on both Si and SiO 2 , an Ar beam is used to irradiate obliquely the pretreated surface. As a result, diamond can no longer nucleate on Si, it nucleates only on one edge of the SiO 2 dots and grows over the Si substrate to about 10 #m. Well defined polycrystals having equal grain sizes have been obtained. The role of the Ar beam irradiation on Si and on SiO 2 is also discussed.

Large area diamond selective nucleation based epitaxy

A uniform large area H2 plasma can be generated by a magneto-activated microwave plasma chemical vapour deposition (CVD) system. This plasma has been employed, instead of the previously used argon beam, in the diamond selective nucleation based epitaxy (SENTAXY) technique as the irradiation beam to fabricate a large area SENTAXY diamond array which has high potential to make good use of CVD diamond in semiconducting and optical devices. By using this nucleation control technique, an investigation focusing on CVD diamond nucleation sites has also been carried out via an ultrahigh voltage transmission electron microscope. It has been found that diamond preferentially nucleates on the area of the substrate with a high density of defects.

Diamond growth on carbon-implanted silicon

Abstract Diamond has been deposited on a silicon surface modified by low-energy carbon ion implantation. Carbon ions, which were excited by an RF discharge of methane diluted with hydrogen gas and were accelerated by 3 kV DC voltage, were implanted into silicon substrates with a dose of 3 × 1016 ions/cm2. The diamond particles grown on carbon-implanted silicon substrates using a conventional microwave plasma chemical vapor deposition system were single crystals with well defined facets. It was found that the nucreation density on this modified-surface was 5.4 times larger than that on a mirror polished silicon surface. These effects can be originated from microscopic diamonds formed in the carbon-implanted layer during diamond deposition. The high quality diamond particles grew up to 20 μm, because microscopic diamonds act like single nuclei for diamond growth.

Persistent hole burning of the nitrogen vacancy center and the 2.16 eV center of chemical-vapor deposited diamond

The persistent spectral hole burning effect has been observed for the nitrogen vacancy (NV) center and the 2.16 eV center in chemical‐vapor deposited (CVD) diamond. This sideband is the first observation of spectral hole burning in CVD diamond. Holes are burned in the inhomogeneously broadened zero‐phonon lines of both the centers by dye lasers. The holes were observed by photoluminescence excitation spectroscopy, with monitoring of the phonon‐sideband emission, at temperatures up to 130 K for the NV center and up to 100 K for the 2.16 eV center.

Cathodoluminescence imaging of semiconducting diamond formed by plasma CVD

Abstract Boron-doped p-type semiconducting diamond formed by plasma-assisted chemical vapor deposition (CVD) shows the same blue cathodoluminescence (CL), having a peak at 2.8–2.9 eV, as that of natiural semiconducting diamond classified as type IIb. In natural type IIb diamond (semiconducting) and in natural type IIa diamond (insulating), dislocations are luminescent regions. In single crystal polyhedrons of CVD diamond it has been observed that the luminescent regions are located at {100} growth sectors, but few are found at {111} sectors. This feature can be explained by the difference in the introduction of crystal defects between the {100} and {111} sectors. This phenomenon in CVD diamond has been discussed in comparison with natural type IIb diamond.

Fabrication of diamond films by a magneto-active plasma CVD using alcohol-hydrogen system

Good-quality diamond films have been synthesized by a magneto-active plasma chemical vapor deposition (CVD) system using the alcohol-hydrogen system. CnH2n+1OH/H2 (n =1 to 3). The regions to fabricate polycrystalline diamond films are similar for all alcohols for the C/H ratios of the original gas mixtures and are independent of the reaction gases. The films have been studied using scanning electron microscopy (SEM) and X-ray photoelectron microscopy (XPS). A quantitative relationship between morphologies of SEM images of diamond films and the full width at half maximum (FWHM) of diamond carbon ls (C ls) core photoemission spectra has been set up for the first time. The FWHM of the C ls XPS peak of the best diamond film is 0.951 eV and is of good value. The FWHM of diamond C ls peak is very sensitive to the morphology of diamond film. Optical emission spectroscopy (OES) of the plasma shows that the growth rate and the FWHM of diamond C ls peak depend on the ratio of carbon and hydrogen in the plasma. OH radicals are shown to play a role on etching of non-diamond phases.

Study of impurities in CVD diamond using cathodoluminescence

Nitrogen ions were implanted into diamond films formed by microwave plasma CVD. A color cathodoluminescence (CL) system were used to investigate the emission centers of as implanted and the subsequent annealed films. A zero-phono-line (ZPL) from the implanted N+ was observed at 3.19 eV. After annealing, a ZPL at 2.16 eV and a strong emission center in the violet region with a ZPL at 3.19 eV and phonon replicas were observed. The color CL images of the annealed films show that an orange-red color emission comes only from the {100} sectors because of the difference in crystal quality between the {100} and {111} sectors.

Fabrication of diamond films under high density helium plasma formed by electron cyclotron resonance

Abstract Helium gas has been employed instead of hydrogen as the carrier gas to fabricate diamond films using a magneto-active plasma chemical vapour deposition (CVD) system at low pressures. Helium plasma has a much higher plasma density than hydrogen plasma and it has been shown that this promotes fabrication of good quality diamond films at low pressures. Using a gas mixture of methyl alcohol and helium, microcrystalline diamond films with a grain size smaller than 500 A have been fabricated. These microsized diamond films have been investigated by employing X-ray photoelectron spectroscopy, and features equivalent to those of natural diamond have been obtained.

Formation of TiN by nitridation of magnetron sputtered Ti films using microwave plasma CVD

The formation of a TiNz/TiSix bilayer by microwave-assisted nitrogen plasma nitridation of titanium film with changing microwave power has been studied. Rutherford backscattering spectrometry, X-ray photoelectron spectroscopy, X-ray diffractometry, and transmission electron microscopy were used to characterize the formation of TiNz/TiSix bilayer and to examine the barrier properties. The results show that the nitrided and silicided Ti layers grow in thickness and increase in concentration according to microwave power increase, and that the samples treated above the power of 200 W have good film properties, and that the TiNz/TiSix/Si structure has good diffusion barrier properties up to ∼500° C for 30 min heat treatment.