Molybdenum-based image sensor promises super-sensitive cameras
13 June 2013
Molybdenite, a possible successor to silicon based semiconductors, could improve the sensitivity of photographic image sensors by a factor of five.
In 2011, a team from the Ecole Polytechnique Fédérale de Lausanne (EPFL) led by Andras Kis discovered the semiconducting properties of molybdenite (MoS2), and they have been exploring its potential in various technological applications ever since.
This promising candidate for replacing silicon has now been used to produce a prototype of an image sensor, which has five times the light sensitivity of current technology.
The objective of the EPFL work was to demonstrate molybdenite's potential in image sensors, and for this reason, the sensor only has a single pixel. But it needs five times less light to trigger a charge transfer than the silicon-based sensors that are currently available. "Our main goal is to prove that MoS2 is an ideal candidate for this kind of application," explains Kis.
This level of sensitivity would open up the huge area of low-light or night photography, without resorting to noise-generating amplification techniques, slowing down the shutter speed or using a flash.
For some specialised domains in which light conditions are often not optimal, such as astro-photography or biological imaging, the advantage is even more obvious. "It would make it possible to take photographs using only starlight," says Kis.
A single-atom layer of molybdenite - a naturally abundant, inexpensive material - requires only a very small electric charge to function. Because of this, it takes much less light energy to reach the threshold needed to generate a pixel.
In addition, the prototype doesn't require any other semiconductors, which should greatly simplify manufacturing processes.
Kis, who has researched the semiconductivity of molybdenite extensively, recently demonstrated its potential in an integrated circuit and, in early 2013, produced a flash memory prototype.