Molybdenum disulfide speeds up amorphous Si detector for medical imaging

Aug. 5, 2013
Berkeley, CA--Two engineers at the University of California, Berkeley (UC Berkeley) have created an amorphous silicon (a-Si) metal-semiconductor-metal heterojunction photodetector with added molybdenum disulfide (MoS2) that they say could speed up medical imaging at low cost.
Shown is an experimental photodetector made out of amorphous silicon and molybdenum disulfide (MoS2). The two semiconductors together form a high-speed photodetector. (Schematic by Mohammad Esmaeili-Rad)


Berkeley, CA--Two engineers at the University of California, Berkeley (UC Berkeley) have created an amorphous silicon (a-Si) metal-semiconductor-metal heterojunction photodetector with added molybdenum disulfide (MoS2) that they say could speed up medical imaging at low cost.1Molybdenum disulfide is well-known as a lubricant sold in auto-parts shops.

Many photodetectors in large-area imaging devices use a-Si because it absorbs light well and is relatively inexpensive to process. But a-Si has defects that prevent the fast, ordered movement of electrons, leading to slower operating speeds and more exposure to radiation. Getting better performance requires more expensive, high-temperature processing, adding to the price tag of the imaging device.

Sayeef Salahuddin and Mohammad Esmaeili-Rad solved this problem by pairing a thin film of MoS2 with a sheet of a-Si. By forming a diode with the a-Si, the MoS2 allows the photogenerated electrons it collects to travel ten times faster through the a-Si. The detector has a photoresponsivity of 210 mA/W for green light -- two to four times higher than usual for a-Si devices.

The researchers say that because these materials are easy and inexpensive to handle, the cost of speeding up photodetectors would be minimal. Unlike conventional semiconductors like Si, MoS2 consists of individual nanosheets that can be torn off like pages in a book. These sheets can be used to make thin, novel electronic devices or to improve existing ones.

The National Science Foundation and the Defense Advanced Research Projects Agency helped support this work. Esmaeli-Rad's postdoctoral fellowship is supported by the Natural Sciences and Engineering Research Council of Canada.

REFERENCE:

1. Mohammad R. Esmaeili-Rad and Sayeef Salahuddin, Scientific Reports 3, article number 2345, 2 Aug. 2013: doi:10.1038/srep02345.

Sponsored Recommendations

Request a free Micro 3D Printed sample part

April 11, 2024
The best way to understand the part quality we can achieve is by seeing it first-hand. Request a free 3D printed high-precision sample part.

How to Tune Servo Systems: The Basics

April 10, 2024
Learn how to tune a servo system using frequency-based tools to meet system specifications by watching our webinar!

Motion Scan and Data Collection Methods for Electro-Optic System Testing

April 10, 2024
Learn how different scanning patterns and approaches can be used in measuring an electro-optic sensor performance, by reading our whitepaper here!

How Precision Motion Systems are Shaping the Future of Semiconductor Manufacturing

March 28, 2024
This article highlights the pivotal role precision motion systems play in supporting the latest semiconductor manufacturing trends.

Voice your opinion!

To join the conversation, and become an exclusive member of Laser Focus World, create an account today!