How can I cut the gold on mica products?
Phasis provides special scissors with a titanium nitride-coating so that you can cut the mica between the gold region without damaging the gold surface. With these scissors, you will minimise edge-fracturing on the mica compared to cutting with standard scissors.This operation has to be done with precaution to avoid touching or bending the gold surface and minimising the number of particles falling on the substrate during the cutting process. However, it can be done relatively easily and should not present major problems.
Do I need to perform a flame annealing with gold on mica from Phasis?
No, and that is a clear advantage for our customers! You do not need to flame anneal the Au111 on mica substrates before using them. Phasis films are freshly grown just before being sent to the customer. The surface is thus of good quality and there is no need for a second annealing process. However, the substrates have to be used in a short time scale after reception.
If I want to flame anneal the substrates anyway, how can I do it?
If you want to anneal the gold surface using an hydrogen annealing procedure, you first place the substrate on a quartz plate and place another quartz piece on the edge of the sample to hold it down. It takes about a minute with a hydrogen flame sweeping back and forth at a rate of approximately 1 Hz. The flame (approximately 4 cm long) should slightly touch the surface. The gold surface becomes a little bit orange and you have to pay attention not to overheat it - that is, when the film glows! Best do it in the dark to have better visual control. Also make sure that all the safety requirements are met. This procedure is under your own responsibility.
Can you grow thicker or thinner gold films on mica?
Phasis has grown films with thicknesses up to 500nm and lower than 200nm. For very thin film, however, the gold surface will present islands with holes in-between, the film being not thick enough to allow a better covering. Films with thicknesses different from 200nm are non-standard products and price and delivery time have to be determined on a case to case basis.
What is epitaxy?
Epitaxy refers to extended single-crystal film formation on top of a crystalline substrate.
How is film thickness verified?
The gold film on mica thickness is controlled using X-ray diffraction analysis. The finite number of diffracting planes leads to oscillations of diffracted intensities whose period is related to the layer thickness. We use the oscillations of diffracted intensities around the 001 peak of gold 111. These oscillations are simulated numerically to estimate the film thickness. The occurrence of finite size oscillations indicates a high degree of crystallinity of the samples. To control the thickness of the Bionano gold, we use the X-ray in the reflectometry mode. Reflectometry is performed in the low angle mode with the x-ray radiation in grazing incidence with respect to the sample. In this configuration, the beam is both reflected by the film surface and by the film-substrate interface, giving an interference pattern observable through oscillations in the reflected intensity. The period of these oscillations only depends on the different refractive indices and on the film thickness, irrespective of whether the film is crystalline or not. The film thickness is the only adjustable parameter to fit the observed oscillations.
Can you briefly describe the procedure to write and image ferroelectric domains using an AFM?
To write the ferroelectric domains, the tip is in contact with the sample surface and the voltage, +10V or -10V, is applied to the tip through the program (using for instance an AFM Digital Instrument (1996) MMAFM-2). Typically a 0.2 Hz scan rates is used. To image the ferroelectric domains the tip is in contact with the sample surface while applying, between the tip and the grounded substrate, an AC bias. Typically, a 1.5V AC voltage at 10kHz is used for the measurement. The AFM tip excites a local piezoresponse, which can be detected using a lock-in technique (Stanford Research Systems lock-in amplifier). The two polarization states respond 180° out of phase with each other, thus allowing a phase contrast image of the domains to be obtained.