Figure 1: A thin movie of cuprous iodide crystals (blue) on an indium arsenide substrate (yellow). The sample’s pureness was evaluated by shining photons onto the surface area to develop electron–hole sets (red and blue spheres) and keeping an eye on the light that was given off (white rays). Credit: © 2021 RIKEN Center for Emergent Matter Science
Better optoelectronic gadgets might be recognized utilizing a top quality movie of cuprous iodide.
A defect-free thin movie of cuprous iodide—comprised of simply one crystal—has actually been produced by RIKEN physicists1. The atomically flat sample is an increase for producing much better semiconductors.
Semiconductors lie at the heart of lots of optoelectronic gadgets consisting of lasers and light-emitting diodes (LEDs). Engineers would enjoy to utilize cuprous iodide—an example of a halide substance—for semiconductors since it is an exceptional conductor that is steady above space temperature level. The problem is that it is difficult to produce a really thin movie of cuprous iodide without pollutants. The normal approach includes transferring the movie from an option. “But a solution process can’t make a high-quality thin film from cuprous iodide,” states Masao Nakamura of the RIKEN Center for Emergent Matter Science.
Instead, Nakamura and his colleagues utilized an alternative method referred to as molecular beam epitaxy, in which the movie is slowly grown on top of a substrate, at a raised temperature level, and in a vacuum. Molecular beam epitaxy is currently typically used in producing semiconductors. But it is tough to utilize for cuprous iodide since the product is extremely unpredictable—significance that it quickly vaporizes throughout the procedure, instead of settling into a movie. To conquer this problem, the group started growing their movie at a lower temperature level and after that increased the temperature level. “This two-step process we newly developed was highly effective,” states Nakamura.
The group had another technique to raise the quality of their movie. They selected indium arsenide as the substrate because its lattice spacing is extremely comparable to that of cuprous iodide. “If the lattice spacing is not well matched, many defects will form in the material,” discusses Nakamura.
Nakamura and his associates then evaluated the pureness of their sample utilizing a method called photoluminescence spectroscopy, which includes shooting photons, or particles of light, at the surface area of the product. These photons are soaked up by the product, amazing its electrons to a greater energy state and triggering them to produce brand-new photons (Fig. 1). Monitoring the given off light enabled the group to identify that they had actually developed a single-crystal movie, devoid of problems. “We expected the quality to improve using our method,” states Nakamura. “But the results exceeded our expectations.”
Nakamura and his group now prepare to sandwich together semiconductors made from various halides and examine brand-new residential or commercial properties that develop. “We will explore emerging novel functionalities and physics at the halide interfaces,” states Nakamura.
Reference: “Heteroepitaxial growth of wide bandgap cuprous iodide films exhibiting clear free-exciton emission” by S. Inagaki, M. Nakamura, Y. Okamura, M. Ogino, Y. Takahashi, L. C. Peng, X. Z. Yu, Y. Tokura and M. Kawasaki, 5 January 2021, Applied Physics Letters.
DOI: 10.1063/5.0036862
