Chunzhi Gong

Publications (9)12.66 Total impact

• Source

  Available from: cityu.edu.hk

  Article: High voltage pulser with a fast fall-time for plasma immersion ion implantation.

  Zongtao Zhu, Chunzhi Gong, Xiubo Tian, Shiqin Yang, Ricky K Y Fu, Paul K Chu
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  ABSTRACT: A novel high voltage (HV) modulator that offers a short fall time to minimize sputtering effects and allow more precise control of the incident ion fluence in plasma immersion ion implantation is described. The use of 36 insulated-gate bipolar transistors in the 30 kV hard-tube pulser reduces the HV fall time to 3.5 μs, compared to a fall time of 80 μs if a pull-down resister is used. The voltage balance is achieved by a voltage-balancing resistor, clamped capacitance, and the synchronization of drive signals. Compared to the traditional method employing a pull-down resister or an additional hard tube, our design consumes less power and is more economical and reliable.
  The Review of scientific instruments 04/2011; 82(4):045102. · 1.52 Impact Factor
• Source

  Available from: 144.206.159.178

  Article: Novel plasma immersion ion implantation and deposition hardware and technique based on high power pulsed magnetron discharge

  Zhongzhen Wu, Xiubo Tian, Jingwei Shi, Zeming Wang, Chunzhi Gong, Shiqin Yang, Paul K. Chu
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  ABSTRACT: A novel plasma immersion ion implantation technique based on high power pulsed magnetron sputtering (HPPMS) discharge that can produce a high density metal plasma is described. The metal plasma is clean and does not suffer from contamination from macroparticles, and the process can be readily scaled up for industrial production. The hardware, working principle, and operation modes are described. A matching circuit is developed to modulate the high-voltage and HPPMS pulses to enable operation under different modes such as simultaneous implantation and deposition, pure implantation, and selective implantation. To demonstrate the efficacy of the system and technique, CrN films with a smooth and dense surface without macroparticles were produced. An excellent adhesion with a critical load of 59.9 N is achieved for the pure implantation mode.
  Review of Scientific Instruments 04/2011; · 1.37 Impact Factor
• Source

  Available from: edu.hk

  Article: A Specially Designed PLC-Based High-Voltage Pulse Modulator for Plasma Immersion Ion Implantation

  Zongtao Zhu, Chunzhi Gong, Zhijian Wang, Xiubo Tian, Yi Li, Shiqin Yang, R.K.Y. Fu, P.K. Chu
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  ABSTRACT: A novel high-voltage pulse power system based on a programmable logic controller (PLC) is developed for plasma immersion ion implantation (PIII). The PLC unit with strong anti-interference ability is utilized to optimize both electrical parameters and ion-implantation processes with manual or/and procedure modes. Specially designed periphery circuits are developed to realize the arbitrary adjustment of pulsing frequency and width which is impossible for conventional PLC systems. The electrical protection can also work rapidly in the case of a sudden short circuit. In the main power circuit, a tetrode hard tube is employed to switch the dc high voltage. In order to reduce the rise time of the pulse as much as possible, the potentials on the tetrode grids are optimized. A closed-loop system is also designed to ensure implantation voltage not to depend on the plasma load during the PIII processes. With the help of numerical calculation or simulation, the expected ion energy-number spectrum can be easily obtained.
  IEEE Transactions on Plasma Science 12/2010; · 1.17 Impact Factor
• Article: Hybrid radio-frequency/direct-current plasma-enhanced chemical vapor deposition system for deposition on inner surfaces of polyethylene terephthalate bottles.

  Jing Li, Xiubo Tian, Chunzhi Gong, Shiqin Yang, Ricky K Y Fu, Paul K Chu
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  ABSTRACT: A hybrid radio-frequency (rf)/direct-current (dc) system has been developed to control the biasing effects during deposition of diamondlike carbon (DLC) films onto the inner wall of polyethylene terephthalate (PET) bottles. An additional dc bias is coupled to the rf electrode to produce the effect of equivalent rf self-biasing. This allows more flexible control of the deposition of the DLC films which are intended to improve the gas barrier characteristics. The experimental results demonstrate that the additional dc bias improves the adhesion strength between the DLC film and PET, although the enhancement in the gas barrier properties is not significantly larger compared to the one without dc bias. The apparatus and methodology have practical importance in the food and beverage industry.
  The Review of scientific instruments 12/2009; 80(12):123504. · 1.52 Impact Factor
• Article: Ion trajectories in plasma ion implantation of slender cylindrical bores using a small inner end source

  Xiubo Tian, Chunzhi Gong, Yongxian Huang, Haifu Jiang, Shiqin Yang, Ricky K. Y. Fu, Paul K. Chu
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  ABSTRACT: Plasma immersion ion implantation (PIII) into slender cylindrical bores with higher efficiency is described in this letter. The use of an inner end plasma source excited by a radio-frequency hollow cathode is investigated theoretically and experimentally. The end source that is covered by a small grounded shielding electrode to ensure steady discharge enables continuous delivery of the required plasmas, and the potential difference in the tube increases the ion impact energy. Particle-in-cell simulation demonstrates that the ion trajectories are complex due to the special electric field configuration that is composed of three regions characterized by ion acceleration, no electric field, and ion deceleration. The end source structure with the open shielding electrode is insufficient to achieve high ion energy, although it is effective in maintaining a steady discharge in the source. Hence, a shielding electrode with a protruding electrode structure is required to conduct high energy PIII; a cylindrical bore with an inner diameter of 20 mm is successfully implanted.
  Applied Physics Letters 11/2008; 93(19):191501-191501-3. · 3.84 Impact Factor
• Article: Direct coupling of pulsed radio frequency and pulsed high power in novel pulsed power system for plasma immersion ion implantation.

  Chunzhi Gong, Xiubo Tian, Shiqin Yang, Ricky K Y Fu, Paul K Chu
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  ABSTRACT: A novel power supply system that directly couples pulsed high voltage (HV) pulses and pulsed 13.56 MHz radio frequency (rf) has been developed for plasma processes. In this system, the sample holder is connected to both the rf generator and HV modulator. The coupling circuit in the hybrid system is composed of individual matching units, low pass filters, and voltage clamping units. This ensures the safe operation of the rf system even when the HV is on. The PSPICE software is utilized to optimize the design of circuits. The system can be operated in two modes. The pulsed rf discharge may serve as either the seed plasma source for glow discharge or high-density plasma source for plasma immersion ion implantation (PIII). The pulsed high-voltage glow discharge is induced when a rf pulse with a short duration or a larger time interval between the rf and HV pulses is used. Conventional PIII can also be achieved. Experiments conducted on the new system confirm steady and safe operation.
  Review of Scientific Instruments 05/2008; 79(4):043501. · 1.37 Impact Factor
• Article: Theoretical investigation of plasma immersion ion implantation of cylindrical bore using hollow cathode plasma discharge

  Xiubo Tian, Chunzhi Gong, Yongxian Huang, Haifu Jiang, Shiqin Yang, Ricky K.Y. Fu, Paul K. Chu
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  ABSTRACT: Plasma immersion ion implantation of the internal surface of a cylindrical bore with a small diameter is difficult. The use of radio-frequency hollow cathode discharge as the internal plasma source for ion implantation is proposed. The implantation dynamics and plasma sheath expansion are investigated numerically using the particle-in-cell model. The inner diameter of the tube in our simulation is 20 mm and the external diameter of the hollow cathode is 12 mm. Three electric field zones are observed due to the existence of the electrode with ground potential in the tube. The ions undergo acceleration in the region close to the hollow cathode, maintain their velocity in the zone without the electric field due to overlapping of the plasma sheath, and decelerate in the region near the open end of the tube. Most of the ions are implanted into the surface away from the open plane of the hollow cathode. This is attributed to the special configuration of vertical electric field. The simulation results have demonstrated that plasma immersion ion implantation using a hollow cathode can be effectively applied to the treatment of the inner wall of a cylindrical bore, especially the ones with a small diameter.
  Surface and Coatings Technology 203:2727-2730. · 1.87 Impact Factor
• Article: High-voltage glow discharge plasma immersion ion implantation assisted by magnetic field

  Xiubo Tian, Chunzhi Gong, Lei Liu, Shiqin Yang, Ricky K.Y. Fu, Paul K. Chu
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  ABSTRACT: Plasma immersion ion implantation (PIII) employing high-voltage glow discharge is an effective tool to achieve better material properties without external plasma sources. The efficacy of high-voltage glow discharge can be enhanced by the use of a magnetic field. Our experimental results disclose that the addition of permanent magnets effectively increases the plasma density and decreases the delay time to ignite the glow discharge. The discharge can also be ignited at a lower pressure in the presence of a magnetic field. This helps to improve the implantation energy due to reduced particle collisions. In addition, the process is more flexible since plasma generation depends less on the gas pressure and target bias compared to conventional high-voltage glow discharge PIII. To demonstrate the advantages of this simple, flexible and efficient technique, polyethylene terephthalate (PET) foils are treated by glow discharge PIII to improve the surface properties and smaller water contact angles are observed from the implanted samples.
  Surface and Coatings Technology.
• Source

  Available from: Andre Anders

  Article: Flexible system for multiple plasma immersion ion implantation-deposition processes

  Xiubo Tian, Ricky K Y Fu, Paul K Chu, Andre Anders, Chunzhi Gong, Shiqin Yang
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  ABSTRACT: Multiple plasma immersion ion implantation-deposition offers better flexibility compared to other thin film deposition techniques with regard to process optimization. The plasmas may be based on either cathodic arc plasmas metal ions or gas plasmas gas ions or both of them. Processing parameters such as pulsing frequency, pulse duration, bias voltage amplitude, and so on, that critically affect the film structure, internal stress, surface morphology, and other surface properties can be adjusted relatively easily to optimize the process. The plasma density can be readily controlled via the input power to obtain the desirable gas-to-metal ion ratios in the films. The high-voltage pulses can be applied to the samples within in-duration mode, before before-duration mode, or after after-duration mode the firing of the cathodic arcs. Consequently, dynamic ion beam assisted deposition processes incorporating various mixes of gas and metal ions can be achieved to yield thin films with the desirable properties. The immersion configuration provides to a certain degree the ability to treat components that are large and possess irregular geometries without resorting to complex sample manipulation or beam scanning. In this article we describe the hardware functions of such a system, voltage–current behavior to satisfy the needs of different processes, as well as typical experimental results. © 2003 American Institute of Physics.