Xianyi Lu

The deposition of diamond film with high thermal conductivity

In this paper, the main factors influencing thermal conductivity of diamond film were analyzed in theory. The thermal conductivity of diamond film was measured by means of the photothermal deflection method. Various crystal structures of diamond films were obtained by synthesis with various deposition methods and conditions. Diamond films synthesized under lower concentration of methane and technique of annealing by MWPCVD method have higher thermal conductivity. Thermal conductivity of diamond film increases with the increasing of removal thickness for the SiC layer on the back of the film. (100)-oriented diamond thick films have higher thermal conductivity.

Effects of Alcohol Addition on the Deposition of Diamond Thick Films by dc Plasma Chemical Vapor Deposition Method

Diamond films have been deposited by dc plasma chemical vapor deposition method. The addition of alcohol in the resource gas largely increases the deposition rate. The effects of alcohol addition on deposition rate and film quality are analyzed by scanning electron microscopy and Raman spectrometry. The mechanism of experimental phenomena is discussed.

Pattern metallization on diamond thick film substrate

Abstract Diamond thick film with high thermal conductivity and high electrical resistivity has been synthesized with DC-hot cathode PCVD and EA-CVD methods. After being cut, polished and cleaned, diamond thick film was used as electronic packaging material. Pattern metallization on diamond thick film substrates was obtained using a thick-film-writing process. Transition metal ink was directly written on the diamond substrate as base ink. Then gold ink was printed on the transition metal ink. After pre-firing in the atmosphere at 450oC for 10 min, the substrate was fired in a vacuum (1.33 Pa) at 850oC for 30 min. Minimal or no gold blistering was observed from the fired diamond substrate, and the gold layer had not peeled after several heat impacts (25∼450oC). The result indicates that the fired metallization pattern has good adhesion to the diamond substrate. The chips were welded easily to the substrate and further electrically connected to the ground, power and signal layers, respectively, by wire bonding. The surface of the metallized substrate was characterized by scanning electron microscopy (SEM) and the carbide layer was analyzed by X-ray diffraction (XRD).

The preparation of (001) textured diamond films with large areas

Abstract The (001)-textured diamond films were deposited on a 4-inch Si wafer by a three-step method. First, fine diamond powder was seeded on the substrate by a dipping method to obtain high diamond nuclei density and low interface state density. Then a H ion etching and annealing was performed for 1 h by setting an electric potential of −120 V to improve the adhesion between diamond and substrate and obtain high (001)-textured films. At last, diamond films were deposited under the condition for (001)-textured growth. A SEM was used to analyze the morphology of diamond crystallites and the film formed with the above three steps and Raman spectra was applied to obtain the phase purity of the films. The results show that large area, low interface state density, uniform and (001)-textured diamond films can be synthesized by this three-step process.

Field-emission characteristics of diamond films deposited by microwave plasma chemical vapor deposition

We have studied the field emission characteristics of diamond films. The diamond films were deposited on mirror- polished silicon substrates by bias enhanced nucleation microwave plasma chemical vapor deposition technique. The nucleation density and surface morphological properties were analyzed by means of SEM. The field emission characteristics of diamond films nucleated on different bias conditions were studied by measuring emission current versus voltage curves (I-V plots). The diamond film has small grain sizes and high nucleation density when bias value is high, it has low turn- on voltage. The diamond film nucleated on higher methane concentration has also low turn-on voltage and its emission current increases rapidly as voltage increases.

Optical properties of boron-doped diamond films

Boron doped and undoped diamond films were prepared by a hot filament method of chemical vapor deposition (CVD). Up to 1020 cm-3 boron concentration was obtained in doped specimens. Infrared (IR) absorption and luminescent emission of diamond films were measured and discussed. Absorption peaks of 1971.3 cm-1, 2020.0 cm-1, and 2161.4 cm-1 were observed in undoped diamond films, which are assigned to two-phonon lattice vibration absorption of diamond. Two absorption peaks at 2850 cm-1 and 2910 cm-1 were usually observed in CVD diamond films, which is very similar to that of C-H vibration absorptions in CH2-radicals. In the range of 300 nm - 800 nm, four typical luminescent emissions were observed, which are 2.76 eV broad emission, 2.34 eV broad emission, 2.16 eV sharp emission with a low- energy shoulder and a sharp emission at 1.675 eV. The 2.34 eV emission is originated from the donor-acceptor (D-A) pairs, the others are originated from defect related centers.