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University of Nebraska–Lincoln

Nebraska Center for Materials and Nanoscience

Faculty - Research Spotlight - Barry Cheung

The research team of Barry Cheung focuses on the nanostructure-induced phenomena in metallic boride material systems synthesized by chemical vapor deposition (CVD). The family of metallic boride materials typically has refractory properties including high melting points, high chemical stability and high hardness. Its members exhibit a wide range of other unique physical properties such as low work function, superconducting behavior and high coercivity. Applications of metallic boride materials range from strong permanent magnets (e.g. Nd2Fe14B), superconductors (e.g. MgB2), electron emission materials (e.g. LaB6) and to even colorful decoration coatings. Judicious choice of chemical reaction schemes is the most important key for successful growth of nanostructured crystalline materials with designed functionalities by CVD. Precise control of chemical reactant flux, reaction temperatures, and appropriate catalyst systems allow the controlled growth of materials with various shapes down to a few nanometers. Such control also allows the creation of multi-layered artificial nanostructures. These quasi one-dimensional nanostructures are expected to exhibit novel physical properties deviated from those of the bulk materials.
Barry Cheung

Controlled growth of high-aspect ratio nanomaterials enables the fabrication of efficient field electron emitters. An important part of Cheung’s present research involves the investigation of the electron emission characteristics of low work function metallic boride nanomaterials in the field emission and ballistic regimes. Recently, low work function metallic boride materials with shapes ranging from nanoobelisks to nanowires of tip diameters down to a few nanometers have been synthesized by Cheung’s team. Presently, they are studying the relationship between geometric shapes and the field emission behavior of these materials.
The major component in Dr. Cheung’s research and training involve the creation of novel nanomaterials and tools for studying these nanoscopic systems. Dr. Cheung was born and raised in Hong Kong SAR of China. He earned his Ph.D. degree at Harvard University, where his research focused on the synthesis and the use of carbon nanotubes for scanning probe microscopy. He joined UNL after his post doctoral training on the study of virus assembly model systems at Lawrence Livermore National Laboratory.
Dr. Cheung’s team of graduate students Joseph R. Brewer, Gonghua Wang, and Wanwan Huang worked together with post doctoral researcher Nirmalendu Deo. Their research focus is the development of refractory metallic boride and boron systems of nanomaterials for efficient high current emitters functioning in the ballistic emission regimes. This research may possibly lead to the next generation of high power nanoelectronics ranging from compact tetra Hertz klystron, parallel electron beam writers to field emission displays.
Trans-disciplinary research in Dr. Cheung’s group is achieved through collaborations with other NCMN members and national laboratories. Recent collaborative work on the design of medical bioceramic films is carried out with Dr. Namavar, Dr. Zeng, Dr. Mei and Dr. Sabirianov. Potential applications of these materials include implant coating and substrate platform for cell growth study. Besides studying the fundamentals for the growth of metallic boride systems, Cheung’s team also investigates the growth kinetics of CVD boron thin films. Through exploiting the conformal boron coating method developed in Cheung’s laboratory, Dr. Cheung’s team collaborates with Lawrence Livermore National Laboratory in the development of pillar-structure-based thermal neutron detectors.
Dr. Cheung’s group applies scanning probe microscopy, electron microscopy, DC and AC electrical characterization under high vacuum, and optical spectroscopic methods to characterize nanostructured metallic boride systems. As a member of the Nebraska Center for Materials and Nanoscience (NCMN), Dr. Cheung’s team conduct the structural and chemical characterization facilities at NCMN and the microscopy facilities at the Center for Biotechnology.

(Spring 2008)