SiOnyx Brings “Black Silicon” into the Light; Material Could Upend Solar, Imaging Industries

Silicon is a wonderfully cooperative element. It takes relatively little energy to promote the electrons in a silicon crystal from their usual, docile orbits around the atomic nuclei into wild, free circulation. That’s what makes silicon a semiconductor—valuable for electronic switching devices such as transistors, sensing devices such as the CCDs in cameras and X-ray machines, and energy-generating devices such as photovoltaic cells.

But silicon would be more wondrous if it were even more responsive—if an incoming photon needed less energy to knock loose an electron, for example, or if a single photon could kick loose many electrons. In pursuit of this vision, chemists, physicists, and engineers have spent decades trying out various ways of modifying silicon crystals—for example, by doping them with atoms of arsenic or other elements that put more free electrons into the mix.

Almost ten years ago, graduate students in the laboratory of physics professor Eric Mazur at Harvard University stumbled across a new way of making silicon more responsive: they found that if they blasted the surface of a silicon wafer with an incredibly brief pulse of laser energy in the presence of gaseous sulfur and other dopants, the resulting material—which they called “black silicon”—was much better at absorbing photons and releasing electrons. And this week, after nearly three years in hyper-stealth mode, a spinoff company with an exclusive license from Harvard to commercialize the process has begun talking with reporters.

Executives for the company, called SiOnyx, believe that its technology will help semiconductor manufacturers build far more sensitive detectors and far more efficient photovoltaic cells, using essentially the same silicon-based processes they currently depend on—thereby revolutionizing areas such as medical imaging, digital photography, and solar energy generation.

The venture-funded startup has emerged with a bang, securing exclusive coverage by New York Times technology writer John Markoff in today’s edition. But SiOnyx CEO Stephen Saylor and principal scientist James Carey, a PhD graduate of Mazur’s lab, also showed me around their Beverly, MA, facility last week, on the condition that this post would appear after Markoff’s story.

SiOnyx principal scientist James Carey (L) and CEO Stephen Saylor (R) “You’ve never been able to detect light the way this stuff detects light,” says Saylor, referring to black silicon’s remarkable sensitivity to incoming photons, especially photons at infrared energies, which pass through normal silicon as if it were transparent. That property could make it an ideal, and inexpensive, replacement for less-sensitive detectors in devices as varied as X-ray and CRT machines, surveillance satellites, night-vision goggles, and consumer digital cameras. “It means that you solve a clear and obvious pain point for a very large number of customers,” Saylor says.

And because black silicon is just silicon that’s been roughed up a bit by femtosecond laser pulses and chemical treatment, SiOnyx’s technology could theoretically be integrated into existing semiconductor fabrication lines without much disruption. “You can do everything we’re talking about without extraordinary, Herculean effort, and you can do it in a way that fits with high-volume manufacturing flows,” says Carey.

SiOnyx was incorporated in 2005, secured the Harvard license in early 2006, and obtained $11 million in venture financing from Harris & Harris, Polaris Venture Partners, and RedShift Ventures in 2007. The company is going public with its story because “we have enough momentum now both with strategic partners and with the technology that it makes sense at this point to share a little more about what we are up to,” say Saylor.

Harvard, for its part, is holding up SiOnyx as one early result of the ongoing overhaul of the university’s technology licensing efforts. The school gained a reputation early in this decade as being unresponsive, even hostile, toward faculty and students who wished to commercialize discoveries made in the university’s labs, especially in areas outside of biotechnology and drug development. For years after the discovery of black silicon in Mazur’s lab, the school’s technology transfer office “wasn’t very excited” about the work, according to Carey.

But in 2005 the university brought in university licensing veteran Isaac Kohlberg to rebuild its technology transfer operation from scratch. Saylor and Carey say it was Kohlberg and his staff who finally understood black silicon’s potential and ironed out the licensing deal that made SiOnyx possible.

“The exciting steps being taken to develop [black silicon] for commercial application serve as even more evidence of the entrepreneurial energy that continues to gel and accelerate at Harvard,” Kohlberg says in a press release set to be issued tomorrow by SiOnyx and Harvard’s Office of Technology Development.

Bob Metcalfe, a general partner at Polaris Ventures who sits on SiOnyx’s board, thinks Kohlberg is right: “Harvard seems to be getting its act together in patent licensing,” he says.

Exactly what makes black silicon such an effective absorber of photons is a question that even Mazur and Carey couldn’t answer at first. The material is one of many offshoots of work going on in Mazur’s lab in the late 1990s using femtosecond lasers—devices that can emit an intense pulse of light lasting only a millionth of a billionth of a second. Mazur lab researchers found that zapping a silicon wafer with such pulses in the presence of sulfur hexafluoride gas—an experiment initially carried out on a whim—left the wafer festooned with tiny cones. Silicon roughened in this way soaks up almost all of the light that strikes it in visible wavelengths, appearing black—hence the name.

“It took several years for us to begin thinking properly about what we had,” says Carey. “The original thought was that the surface roughening process was what created the advantage.” The researchers hypothesized that photons were bouncing from cone to cone—and that the more times they bounced, the higher the likelihood that they’d be absorbed, thus dislodging electrons. But then Carey and his coworkers realized that black silicon was also absorbing infrared light, “which you can’t explain just by … Next Page »

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Wade Roush is the producer and host of the podcast Soonish and a contributing editor at Xconomy. Follow @soonishpodcast

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  • Would it help you to know that an elecron is a helical string wave of one over Planck’s constant, 1/h, cubed or about ten to exponent 79, and that the photon as Einstein’s E = hf is the smallest discrete element of light and all other energy so that it is synonymous wih quantum energy h, when the pulsing is 1 photon per second; or even better still that the Planck relation E = nhf always anthropic measures with n = 1/h—to finally explain why measure energy and frequency are always numerically the same? And that what we call mass is always h-discretely equal to nh by consistent anthropic measure definition, that quantum mass is 1/h grams and that it is precisely the necessary constant mass of all electrons?
    In other words, E is identical to nhf is idential to Mf is identical to M(v-squared) as linesr energy—for all radiation of whatever frequency?

  • jonnyo

    It would not help me at all to know that.

  • mrbill

    No.

  • Robert Grenetz

    I look forward to ISO 6400 cameras with the noise/grain level of the ISO 100 of today. I assume that it should come to market in about 8-10 years. But, what’s being developed with your approach will set up that possiblity.
    In the meantime, good luck with your development.

  • Just Me

    Every article for new solar cells I’ve seen gives an efficiency rating in a percent. What is the efficiency rating on this?

  • draq wraith

    Imagine what they could learn if they would hire a few laser guru’s that understood quantum mechanics, and licensed a 12 year olds 3D solar cell technology and added it to the mix.
    I suspect if we could make this cell act in 5 dimensions shaping it according to the light source on the various sides we would have upward 90% efficient solar cells.

    D~W

  • Time Drifter

    re: “Would it help you to know that an elecron is a helical string wave of one over Planck’s constant, 1/h, cubed or about ten to exponent 79,…” Aren’t physicists supposed to use units? 10 to the 79th what? Wave of what?

  • The currently publicly-traded solar power companies have all taken a drubbing with the rest of the falling market. However, they were struggling even before the subprime crisis really started to take hold of the public’s imagination. Could this be a sign that the market already perceives a resultant over-capacity of solar power generation or a difficult path to profit?

  • NA

    I worked in a team that created “black silicon” for about a year. There are still a few groups who make “black silicon” but as far as what they claim I am not sure if anything will come of it. I left the team because silicon becomes damaged beyound repair after the laser treatment and the increase in absorption comes for incorporation of sulphur. The sulphur evaporates very easily if one tries to in any way anneal the silicon to make its proporties more controllable. Semiconductor industry spent half a centruy controlling the properties of silicon for a reason. Even in non traditional IR sensor like PbS, the deposition process is controlled. Not absolutely random.

  • davidk

    And imagine what they could have learned and how much sooner they could have learned it if they had consulted film manufacturers who have known for nearly 100 years that intentionally inserted impurities can be extremely beneficial to making better photo-reactive materials.

  • buona sera ,vorrei sapere se questo “silicio nero” verrà messo in produzione, come facciamo a sapere la ditta che produrrà i pannelli e quando si potranno acquistare?
    Ringrazio anticipatamente , e invio i miei più cordiali saluti.
    Renzo Piacentini.

  • Natcore is taking care of many of the problems . Solar is now on its way to pareity