Imaging could get speed boost from auto lubricant

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 - photodetector
Schematic of experimental photodetector made out of amorphous silicon and molybdenum disulfide (MoS2). The two semiconductors form a high-speed photodetector.
Source: Mohammad Esmaeili-Rad / Scientific Reports

There’s not a lot of crossover between car parts and medical imaging components, but a pair of engineers at the University of California, Berkeley, has discovered that molybdenum disulfide (MoS2), commonly used as an engine lubricant, could help speed the photodetectors in large-area imaging devices.

Sayeef Salahuddin, PhD, and Mohammad Esmaeili-Rad, PhD, found that the combination of MoS2 and amorphous silicon (a-Si), a widely used sensing element in photodetectors, created a diode with a photoresponse rate 10 times faster than a-Si alone.

“The device could find applications in large area electronics, such as biomedical imaging, where a fast response is critical,” wrote Salahuddin and Esmaeili-Rad in an article outlining their work published in Scientific Reports.

While commonly used, a-Si is limited by inherent structural defects which cause persistent photoconductivity and lead to slow operation speed and image retention. This is especially an issue is high-speed applications such as fluoroscopy and tomography, according to the researchers, and a faster photodetector like the one they are working on could have a huge impact in such applications.

“The fast response also allows shorter x-ray exposure times to patients which helps to reduce the health hazards of x-ray radiation,” they added.

Salahuddin and Esmaeili-Rad’s device is a heterojunction photodetector consisting of a thin film of MoS2 and a sheet of a-Si. Photo-generated electrons are able to move through the device quickly, and the photodetector has rise and fall times of about 0.3 ms. It has a photoresponsivity of about 210 mA/W at the wavelength of 550 nm, according to the researchers.

Since the materials are cheap, the cost to upgrade photodetectors would be minimal, they added.

In addition to medical imaging, the MoS2 could also have applications in solar cells and energy-efficient transistors.