Crystals mounting and handling

To exploit this latter alternative, mica sheets were cleaved from larger crystals of Muscovite mica until a thickness of the order of 1-5 pm was reached as judged by the brightness and color of the fringes seen under room light. Actual film thickness was determined from the infrared fringe spacing. Mica at these thicknesses is delicate but can be handled if care is taken it is possible to cleave mica to thicknesses below 1 pm but at these thicknesses the mica becomes too delicate to use unsupported. The cleaved mica sheets were mounted in standard transmission holders constructed from Teflon. 

Crystals that are oifly moderately unstable can be handled using the oil drop method,which became popular in the last decade. This method is extremely convenient and easy, obviating the need for glove boxes and other comphcated mounting devices. The crystals are prepared in a Schlenk vessel which is connected to an inert gas (N2 or Ar) fine, creating an excess pressure inside. Then it is possible to... 

Fig. 2 QCM-D measurements. The key components are (i) the sensor crystal (QCM) mounted in a measurement chamber with facilities for batch or flow mode measurements in liquid or gas, (ii) the drive electronics (relay and signal generator) and (hi) the recording electronics (probe, reference frequency, filter) including data-handling and software (analog-to-digital converter and computer)...

Cooling may also reduce any decomposition of the sample in the X-ray beam, which imposes some thermal loading on the crystal through absorption effects. Furthermore, it is far easier to handle air-sensitive materials in this way than for room-temperature data collection. Instead of having to provide such crystals with a stable and robust protective shield (either a coating such as epoxy resin, or a sealed thin-walled capillary tube), they can simply be handled under an inert viscous oil into which they are introduced from a Schlenk tube. The oil serves as an adhesive for mounting the crystal on the diffractometer and forms a thin protective film that vitrifies by shockcooling in the cold gas stream. Air-stable and air-sensitive samples can be handled in virtually the same way. 

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