Hi Ron, you seem really enthusiastic about this project. I'm wondering about this part: "This will require a full characterization, with special attention to write/erase lifetime, switching times, power dissipation, and data retention, added to which must be the optical characterization for each step in the development -- all of which is a non trivial undertaking." What do you think the biggest challenge will be to moving characterization forward? Do we have the T&M tools to handle this?
Janine I am certainly excited about the possibility of using these devices as intra and inter chip optical switches and the range of possible products the work might spawn. I think the first step and challenge must be to produce large numbers of planar discrete ITO/GST/ITO PCMs with 7nm GST films. I think the tools for electrical characterisation of those devices are readily available see http://www.eetimes.com/author.asp?section_id=36&doc_id=1323076 and there is a good experience base to draw on. If it was me, I would initially concentrate on those measurements. Then add the platinum mirror and start looking at the optical characteristics when some reasonable level of repeatability and stability has been achieved. Or even do both things in parallel. I guess the simplest optical experiment would be to fabricate the discrete devices with the GST in the amorphous state and use a hot plate to crystallize the material and explore the reproducibility of the colour change. Then do the same experiment after some fixed number of write/erase cycles. I think it is going to get very interesting when the time comes to do the equivalent of PCM elevated temperature data retention, which I suppose we will have to call elevated temperature colour retention for the Opto-PCMs (OPCMs).
Another potential kind of optoelectronic application of phase-change alloys (PCA) can be in permanent interconnections within and between IC chips. For example PCA can be used in ultra-cheap interposers for 2.5D- and 3D-IC assembly (http://www.smta.org/knowledge/proceedings_abstract.cfm?PROC_ID=3898).
Semyon; Thanks for the reminder. I cannot find a copy of the paper in my personal archives. From memory, I thought that work was for permanent face-to-face bonding, or surface mount, implying the bonded chip would be smaller than the chip to which it was bonded to enable connections to the package and then on to the outside world. Also was the beam IR and focussed through the silicon or from the side??? Perhaps you could share with EETimes readers a little more detail. Another personal opto application, a long time ago (applied 1968) I did obtain a patent (US 3,634,927) for writing, using a laser or light beam, crystallized lines of conducting interconnect on an IC which had been pre-coated with an insulating amorphous or phase change material. I think that was the precursor to the work where light was used to write crystallized data on discs.
I think the work I reported in my article above is about is eventually switching and redirecting modulated beams of different colors.