The samples we may study in this SPM lab are almost exclusively solids. They must tolerate Ultra-High Vacuum (base pressure in the experimental chamber is 5E-11 mbar), and upside-down geometry, i.e. samples are facing DOWN during scanning, see image below. Therefore, no liquid/water environment can be provided for the moment. The possibility for studying soft matter or powder samples must be assessed before the experiment time is granted. For STM studies samples must be conductive or semiconductors with resistivity no more than 1 Ohm*cm3 (doping level of around 10E16 cm-3 for Si). The samples should be as good polished as possible, preferably to mirror finish, in order to allow for fast and reliable tip approach.

 

The sample transfer system is based on standard flat flag-type sample plate, see below.

 

Picture
Standard sample dimensionsLinear size 3-12 mm
Height < 5 mm
Linear size 3-12 mm
Height < 5 mm
Diameter < 10 mm
Height < 5 mm
Wafers 7-10 x 2-5 mm
CommentsStandard flag-type sampleholder. Available in SS or molybdenum, may feature four holes (M1.2) for sample mounting, or a central hole more efficient e-beam heating. Home-built new standard flag-type SH. Available in molybdenum. Features 4 M1.2 threaded holes for sample mounting.Home-built SH for efficient e-beam heating and precision temperature control. Features a K-type thermocouple attached to the sample.Standard Omicron double-stage SH for Si wafers. Direct current heating.

Image courtesy: Scienta-Omicron, GmbH.
DC heating flag type sampleholder

 

Therefore, sample size MUST NOT EXCEED 12 mm in diameter/diagonal and 5 mm in thickness. The minimal size of the sample is dictated by necessity of convenient and stable mounting on the sample plate AND relaible positioning of the scanner tip. In place, we can fast and safely mount samples in down to 5 mm in diameter. Thiner samples might require a custom sampleholder. An example of a GOOD sample size is a disc (preferably, hat-shaped or LEEM-shaped) of around 8-9 mm diameter and 2-3 mm thick OR a wafer 8×5 mm wafer 0.5-1.5 mm thick.