Zengsun Jin

Characteristics of electric parameters in aluminium alloy MAO coating process

Characteristics of electric parameters in the microarc oxidation (MAO) process of aluminium alloy at constant voltage were studied by a homemade data collecting system. The experimental results show that (1) the variations of the cathodic and anodic current amplitudes and the effective working current reflect obviously five different stages in the course of treatment and (2) variations of the dynamic forward resistance and electric resistivity of coatings have different stages too, while changes of the dynamic backward resistance and resistivity with treatment time are not evident. During the MAO process, the dynamic forward resistance is not equal to the backward resistance at any time, and the former is generally greater than the latter. Scanning electron microscopy analysis shows that these changes are attributed to variations of the coating porous structure during different treating times.

Effects of radio frequency power on the chemical bonding, optical and mechanical properties for radio frequency reactive sputtered germanium carbide films

Germanium carbide (Ge1−xCx) films have been prepared by radio frequency (RF) reactive sputtering of a pure Ge(111) target in a CH4/Ar mixture discharge, and their composition, chemical bonding, optical and mechanical properties have been investigated as a function of RF power. The relationship between the chemical bonding and the optical and mechanical properties of the Ge1−xCx films has been explored. The results show that the refractive index of Ge1−xCx films increases from 1.9 to 3.2 and the optical gap decreases from 1.9 to 1.0 eV as RF power increases from 80 to 250 W, which is due to an increase in the germanium content with increasing RF power. Also, it is found that the hardness of Ge1−xCx films increases with increasing RF power, which can be attributed to an increase in the fraction of sp3 Ge–C bonds at the expense of the sp2 C–C bonds in the Ge1−xCx films.

The temperature and radiation properties of silicon devices on diamond

Abstract Microwave plasma chemical vapor deposition (MWPCVD) and annealing technology were used to synthesize diamond film with high resistivity and thermal conductivity. Silicon on diamond (SOD) structure wafer was utilized. Complementary metal-oxide-semiconductor field effect transistors (CMOSFET) were fabricated with SOD wafer. The total-dose radiation and recover characteristics of CMOS/SOD devices were studied by using a cobalt-60 radiation resource, the high temperature properties of this device were also studied up to 350 °C. Comparing with the same device made by bulk silicon wafer, the result of experiment shows that total-dose radiation and high temperature introduce little effect in drain current for the SOD device; the effects of radiation could recover more rapidly under the condition of annealing than that of the bulk silicon device.

Growth of (100) orientation diamond film deposited by MWPCVD methods using the gaseous mixtures of CH4, CO and H2

Abstract Diamond films with a polycrystalline structure have been synthesized on a silicon substrate using the gaseous mixtures of methane, carbon monoxide and hydrogen using the method of microwave plasma chemical vapor deposition (MWPCVD). The growth characteristics of the diamond film were studied by SEM technology and X-ray diffraction. The experimental results show that gaseous mixtures of methane, carbon monoxide and hydrogen at appropriate proportions and concentrations [H2:CH4:CO = 100:1:(1–10), H2 flow is 100 sccm] are advantageous to the deposition of (100) textured diamond film and rotating substrate is beneficial to obtain diamond films with uniform growth. The nature of the substrates used in the experiments has no appreciable influence on the orientation of the diamond films. High quality diamond films of 1 inch in diameter, with uniform growth and (100) orientation were synthesized using suitable conditions.

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).

Electron emission from diamond thin films deposited by microwave plasma-chemical vapor deposition method

Abstract Diamond films with different crystal structures, morphologies and surface characteristics were synthesized under various deposition parameters and annealing conditions by the microwave plasma chemical vapor deposition (MWPCVD) method using gas mixtures of CH4, CO and H2. The effects of CH4 concentrations, grain sizes, grain orientations, film thicknesses and annealing technologies in various ambient gases on planar electron emission of diamond films were studied. The results show that small-grained and (011)-oriented diamond films deposited under the condition of high CH4 concentration present the properties of high emission current and low threshold voltage; the emission current increases with decreasing the film thickness. There are largest current density and lowest threshold voltage at the film thickness of 1.5 μm. The annealing in H2 after deposition appears to be more beneficial in lowering the threshold voltage, increasing emission current and improving stability for electron emission of films than annealing in N2 or Ar. These results indicate that diamond thin films with high emission current, low threshold voltage and high stability can be obtained by selecting suitable deposition parameters of diamond films.

Twin-step-related growth phenomena of thick diamond film

Abstract A thick diamond film prepared by glow discharge plasma assisted chemical vapor deposition (CVD) was investigated by scanning electron microscopy, X-ray diffraction and Raman spectroscopy. The degeneration of the {111} faces into three {110} faces was found to be widespread. Both the {110} and {100} faces grow via a step mechanism, with the steps generally originating from the re-entrant corner formed by twinning. The {100} penetration twin on {100} surfaces is discussed in detail. A twin-step growth mechanism of thick diamond film, which explains the formation of cleavage steps on fracture surface, is proposed.

The radiation hardness properties of γ-ray for SOD circuits fabricated on 4-inch SOD wafer

Abstract A silicon-on-diamond (SOD) structure wafer with 4-inch diameter was fabricated. First, a high quality and low interface state density diamond thin film was uniformly deposited on 4-inch Silicon (001) wafer. Second, continuous H + ion bombardment to as-grown film surface under DC bias was performed to decrease the intrinsic tensile stress in the film. Then, bonding technology of Si wafers was applied for forming the hold of SOD structured wafer. Finally, after the single crystal silicon wafer under diamond film was thinned by a machine method and polished by using chemical and ion beam methods, an active SOD wafer with a 0.4–1-μm Si layer was formed. The SOD circuits fabricated on SOD wafer presents very obvious ability of radiation hardness to γ-ray total and instantaneous doses than those of bulk Si circuits.

Total-dose hardness integrated circuit fabricated with silicon-on-diamond structured wafer

Abstract In this paper, we fabricated an integrated circuit with silicon-on-diamond (SOD) structured wafer. The total-dose radiation characteristics of this SOD circuit was studied using a cobalt-60 radiation source. Comparison with the same circuit using bulk silicon wafer, showed that total-dose radiation introduces a small decrease in threshold voltage and drain current to the SOD circuit.