Manufacturing Bits: July 5

World’s largest telescope; neutron scattering; nanowires.


World’s largest telescope
China stunned the industry last month, when the nation rolled out the world’s fastest supercomputer. The system, dubbed the Sunway TaihuLight, is based on processors made in China, not Intel or other U.S. chipmakers.

Now, China has nearly finished the construction of the world’s largest radio telescope. The system, dubbed the Five-hundred-meter Aperture Spherical radio Telescope (FAST), makes use of 4,450 reflecting panels. It’s roughly the size of 30 soccer fields.

A view of FAST (Image by NAOC)

A view of FAST (Image by NAOC)

Located in southwest China’s Guizhou province, the telescope will break the record in terms of the largest system. It will overtake Puerto Rico’s Arecibo Observatory, which is 300 meters in diameter.

The telescope from China will be completed 5-1/2 years after the nation broke ground on the system. The total cost is estimated to be 1.15 billion yuan ($180 million). “FAST will enable Chinese astronomers to jump-start many scientific goals, such as surveying the neutral hydrogen in the Milky Way, detecting faint pulsars, and listening to possible signals from other civilizations,” said Nan Rendong, the general engineer and chief scientist of FAST, on the Chinese Academy of Sciences (CAS) Web site.

The official completion date is set for late September. The telescope’s first data is expected to arrive at that time.

Neutron scattering
China will soon open the nation’s first neutron scattering platform. The system, dubbed the China Spallation Neutron Source (CSNS), is located in the Guangdong Province in southern China.

The neutron itself is a subatomic particle. It has no electric charge and a mass slightly larger than a proton. Neutrons react in different ways to various materials.

Neutron scattering is a non-destructive imaging technique. Typically, a beam of neutrons hits a sample. Some neutrons will go through the sample. Some will hit and interact with atomic nuclei. Those will bounce away at an angle, which is neutron diffraction or scattering. With this, researchers can investigate nature of materials.

The CSNS system could advance the field of neutron imaging. It consists of an H-linac and a proton cycling synchrotron. It is designed to accelerate proton beam pulses to 1.6 GeV kinetic energy at 25-Hz repetition rates. It is set to open in 2017 or 2018.

Making nanowires
China’s Institute of Semiconductors (IOS), part of the CAS, has developed a new approach to grow nanowires on silicon.

Using a two-step approach, researchers fabricated GaSb/GaAs axial heterostructural nanowires on silicon. They also devised tunable GaAsxSb1-x ternary nanowires.

The two-step technology could solve some major problems. III-V materials are attractive for several reasons. For one thing, they could enable high carrier mobility in the channels of chips, thereby providing faster devices.
Nanowire FETs, or the gate-all-around FET, is supposedly the next-generation transistor type. It’s an evolutionary step from today’s finFETs.

The problem? Silicon-based nanowires may or may not provide the best performance for nanowire FETs. III-V nanowires could solve the problem, but there are lattice mismatches between silicon and III–V materials.

In response, the IOS has expanded the temperature window for Ga-catalyze GaAs nanowires. Using molecular beam epitaxy (MBE) tools, researchers have devised a two-step approach for Ga-catalyzed GaAs nanowires growth on silicon. Previous works were limited by a one-step approach and thus growth temperature was confined in a narrow region.