New Material Improves Camera Sensitivity

A new material with five times the light sensitivity of current silicon-based sensor technology could yield cameras sensitive enough to capture photos using only starlight.

All digital cameras work under the same principle: they convert light into an electric charge using a sensor made up of millions of cells, or pixels, on a semiconducting material surface. Each of the pixels reacts to incoming light by generating a specific electrical charge, which is transferred to the camera’s firmware for processing. The efficiency of this process depends on the quantity of light needed to trigger the charge transfer.

In 2011, Andras Kis and colleagues at École Polytechnique Fédérale de Lausanne discovered a naturally abundant, inexpensive material with fascinating semiconducting properties called molybdenite (MoS₂), and have been exploring its potential in various technological applications since (See: Si Alternative is Better Than Graphene). Now this promising candidate for replacing silicon has been integrated into a prototype of an image sensor, yielding five times the light sensitivity of current technology.

A prototype of the first molybdenite-based image sensor, which is five times more sensitive than current silicon-based technology, its creators at École Polytechnique Fédérale de Lausanne say. Courtesy of EPFL/Alain Herzog.

The sensor has only one pixel, a single-atom layer of MoS₂ requiring a very small electric charge from a battery to function. Because of this, it takes much less light energy to reach the threshold needed to generate a pixel — five times less light than its silicon counterpart.

In addition, Kis explains, the prototype doesn’t require any other semiconductors, which should greatly simplify manufacturing processes.

“Our main goal is to prove that MoS₂ is an ideal candidate for this kind of application,” Kis said.

The material’s level of sensitivity could pave the way for low-light or night photography, without resorting to “noise”-generating amplification techniques and specialized domains such as bioimaging and astrophotography where light conditions are not optimal.

“It would make it possible to take photographs using only starlight,” he said.

The technology — described in Nature Nanotechnology (doi: 10.1038/nnano.2013.10) — also has been demonstrated in an integrated circuit and, in early 2013, a flash memory prototype.

For more information, visit: www.epfl.ch