New discovery - GaN hardness diamond

At present, gallium nitride (GaN) has become one of the most important and widely used semiconductor materials. Its photoelectric properties and mechanical properties make it an ideal choice for a variety of applications, including light-emitting diodes, high temperature transistors, sensors, and biocompatible electronic implants.

Three Japanese scientists won the 2014 Nobel prize in physics for their discovery of the important role of GaN in the production of blue light LED lamps. Red light and green light to produce white LED light source, Blu ray is essential.

Recently, four Lehigh engineers reported an unknown attribute GaN: close to the wear resistance of the diamond, but also for the touch screen, the aircraft and the RF microelectromechanical system (RFMEMS) application of the high speed and high vibration technology opens up new markets.

In August, the research team published their findings in the Applied Physics Letters (APL), entitled "Ultralow wear gallium of nitride". The author of the article is mechanical engineering doctoral student Ceng Guosong, Nelson Tansu, DanielE. '39, director of the center for Photonics and electronics (CPN), Department of electrical and computer engineering, visiting professor Patricia M.Smith, Department of mechanical engineering and mechanics Brandon A.Krick, assistant professor, Department of electrical and computer engineering Clarkson University Assistant Professor Dr. Chee-Keong Tan' 16.

The first author Zeng said: "the electronic and optical properties of GaN in recent years has been widely studied, but in fact in its tribological properties, mechanical wear resistance of reciprocating sliding exerting almost no research. Our team is the first to study the wear resistance of GaN, and found that the wear rate is close to the known hard diamond. "

The wear rate is expressed as mm3/Nm. In fact, the wear rate of chalk is about 102mm3/Nm, almost no wear resistance, and diamond wear rate between 10-9 and 10-10, eight times higher than the rate of wear of chalk. The wear rate of GaN is between 10-7-10-9 and 3 to five orders of magnitude higher than that of diamond, which is higher than that of silicon (10-4).

The researchers at the University of the sea used dry sliding wear tests using custom Micro Friction pins to measure the friction coefficient and wear rate of GaN, and the results surprised them. They wrote in the paper that when we wear measurements of unknown materials, we usually slide 1000 cycles and then measure the wear marks. In order to be able to be measured by an optical surface photometer, the experiment has been improved to 30000 cycles. In the wear rate (about two orders of magnitude) in a large range, you can gain insight into the wear mechanism of GaN. The wear rate range is affected by several factors, including environmental factors and crystal orientation, especially the influence of humidity.

"For the first time, we observed that the wear rate of GaN was low in winter, while in summer, the wear rate increased by two orders of magnitude, and the results could not be repeated. "Zeng says. In order to study how the high humidity in summer affects the wear properties of GaN, the researchers put their friction gauges in a glove box that can be filled with nitrogen or moist air. "We observed that the wear rate of GaN increased as we increased the humidity in the glove compartment. "Zeng says.

In October, Orlando of Florida, a nitride semiconductor international seminar, Zeng made a speech about the sea project (IWN2016), titled "Wear of Nitride Materials and Properties of GaN-based structures". Zeng is one of the seven speakers and is the only one to discuss the wear properties of GaN group III nitride materials.

GaN more than and 10, a Tansu and tribology expert, Krick, was intrigued by the GaN's wear performance when they discussed their research project at the faculty meeting of the faculty a few years ago. "Nelson had asked me if someone had studied the friction and wear properties of GaN," Krick said. "I said I didn't know. Then we looked at it and found a vast area. "

Tansu said: "our team found that the hardness and wear resistance of GaN will have a huge impact on the electronics and digital products industry. In a device such as a smart phone, electronic components are placed under the protective coating of glass or sapphire, which raises the issue of compatibility, and the use of GaN can avoid potential compatibility issues. The wear resistance of GaN provides us a way to use a single layer of semiconductor material with excellent optical, electrical properties and wear resistance. With GaN, you can build a complete device on a platform that does not have multiple layers of technology, as well as the integration of electronic, optical sensors and optical transmitters, which will provide a new paradigm for the design of the device. And because GaN can be done very thin and high strength, which will accelerate the development of flexible electronics. "

"GaN is not only a good wear resistance, but also has a good radiation resistance, which is an important attribute of solar powered spacecraft. In the outer space, these solar cells will encounter a large number of cosmic dust, together with X - rays and gamma rays, thus requiring a wear resistant coating, and at the same time, it is compatible with the electronic circuitry of the battery. Without considering the compatibility with the circuit, GaN can provide the necessary hardness. "Zeng says.

In order to better understand the interaction between GaN and water contact, the sea has been working with the team of Princeton University, Professor of chemistry and biological engineering, surface chemistry expert BruceE.Koel. Koel was originally the sea university