Low-Temperature Flexible Sensors Use Ink-Jet Patterning
Anne L. Fischer, Photonics LED Focus, October 2007
Excerpts from the article:
Flexible electronics are used in supermarket labeling and in identification tags and could be used in large sensors for scanning cargo or packaging. As flexible electronics find their way into new applications, manufacturers are faced with problems that include high-cost processing, brittle materials, large-area scaling and more.
Active-matrix amorphous silicon image sensor arrays are the workhorses for large-area sensor applications such as x-ray imaging...The problem is that the thicker the sensor layer is, the more susceptible it is to cracking and breaking. Currently these arrays all are fabricated on glass, but a group of researchers at Palo Alto Research Center in California, has been working with sensor arrays fabricated by plasma-enhanced chemical-vapor deposition on glass and on flexible polyethylene naphthalate substrates...According to William S. Wong, senior member of the research staff at the center, the goal was to get the backplane to perform to specifications normally seen for high-temperature devices on glass.
An added challenge was to keep the sensor’s dark current from increasing as the thickness decreased. Tse Nga Ng, postdoctoral researcher at the center, indicated that, because thinner sensor films could lead to increased current leakage, the problem became finding a film thick enough so as not to jeopardize performance but thin enough to reduce mechanical stress...
This current research is in its last year as a National Institute of Standards and Technology Advanced Technology Plan project in which the researchers worked with Varian Medical Systems of Palo Alto to develop novel sensor materials. The next step in this research is to develop large-area image sensors for cargo scanning, with the goal being to reduce the cost of large-area panels that will be used in US ports of entry.
--Applied Physics Letters, Aug. 6, 2007, 063505
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