Weizhong Tang

Effect of nitrogen ion implantation on the microstructural transformation of boron film

Abstract The structural transformation by nitrogen ion implantation into boron film as a function of film thickness, implant voltage and nitrogen ion dose was systematically investigated. Boron films were deposited on single crystal Si substrates using the electron beam evaporation of pure metallic boron, the thickness being 200, 500, 1000 and 2000 A, respectively. The films were then nitrogen ion-implanted at 25-, 50- and 75-kV implant voltages applied to substrate, respectively, for a fixed nitrogen ion dose of 3×1017 cm−2, and at 1×1017, 2×1017 and 3×1017 cm−2 nitrogen ion doses, respectively, for a fixed implant voltage of 50 kV. The nitrogen ion-implanted boron films were characterized by Fourier transform infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS). XPS results showed that the nitrogen ion-implanted boron films were nitrogen-deficient. Boron exists in the form of both metallic boron and boron nitride as indicated by XPS B1s bands. FT-IR spectra revealed that amorphous boron nitride (a-BN) or hexagonal boron nitride (h-BN) formed during nitrogen ion implantation into boron films. As implant voltage and nitrogen ion dose increased, amorphous BN was initially formed, while h-BN occurred at greater implant voltage and nitrogen ion dose. The thinner film led to the formation of h-BN at a relatively low implant voltage and nitrogen ion dose.

Development of cylinderical cavity type microwave plasma chemical vapor deposition reactor for diamond films deposition

Summary form only given. While microwave plasma chemical vapor deposition (MPCVD) method remains the only option to prepare high quality diamond films, low deposition rate remains the primary concern of the technique. Up until now, there has been a continuous search for new and more efficient high power MPCVD reactors. In this paper, a new cylindrical cavity type MPCVD reactor operated primarily on TM021 resonant mode will be described. To optimize the MPCVD reactor, a phenomenological method has been used, to systematically simulate distributions of both microwave electric field and hydrogen plasma. And then, experiments were conducted to demonstrate that with the newly built MPCVD reactor, a high input microwave power of 8 kW could be reached, and at this microwave power level, high quality diamond films could be deposited at a rate of more than 3 μm/hr.

Development of cylinderical cavity type microwave plasma CVD reactor for diamond films deposition

While microwave plasma chemical vapor deposition (MPCVD) remains the first choice to prepare high quality diamond films, low deposition rate remains the primary concern of the technique. Up until now, there has been a continuous search for new and more efficient high power MPCVD reactors. In this paper, a new cylindrical cavity type MPCVD reactor operated primarily on TM021 resonant mode will be described, and a phenomenological method is used to simulate the distribution of both microwave electric field and hydrogen plasma in the reactor. Experimental results demonstrate that with the newly built MPCVD reactor, a high input microwave power level could be used, and high quality diamond films could be deposited.

Nitrogen in diamond films grown by direct current arcjet plasma process using gas recycling

The nitrogen in polycrystalline diamond films prepared using the direct current arcjet plasma process has been studied using scanning electron microscopy, X-ray diffraction and electron spin resonance (ESR). The ESR spectrum of single substitutional nitrogen was observed, whose intensity showed that the spin concentration decreases with an increase in the substrate temperature. The preferentially orientated growth is influenced by nitrogen. The result indicates that nitrogen plays a special role in the formation and structure of the polycrystalline diamond films studied in this report.