Conventional Sample Preparation

The bulk sample is cut by utilizing a diamond wire saw with a steel wire covered with small-grained diamonds that provide sharp-edged and uniformly cut surfaces. The positioning of the cut and the cutting speed are manually adjustable.

The aim of grinding and polishing steps is to pre-thin the bulk sample down to the desired thickness for the following dimpling and ion milling. For this purpose, silicon carbide abrasive paper disks with grit sizes ranging from 800 to 4000 can be used. Both, the grinding and polishing speed, as well as the pressure of the sample on the rotating abrasive paper disc can be manually controlled. Using grinding and polishing pastes in combination with different solvents helps to optimize the sample’s surface and to remove material gently.

The high-precision grinding and polishing MultiPrep™ System allows semiautomatic preparation of ultra-thin TEM-specimens. Flexible sample positioning enables parallel polishing, wedge polishing or site-specific polishing. The grinding  and polishing parameters rotation speed, oscillation and pressure of the sample on the rotating abrasive paper disc are fully adjustable and can be suited to the requirements of the sample material and/or particular preparation technique. Quantification of the material removal can be real-time monitored with a help of  digital indicators.

The Gatan 656 Dimpling Grinder enables mechanical thinning and polishing of the central area of the pre-thinned sample disk. The desired specimen thickness is achieved by grinding and polishing with the aid of different metallic and felt wheels in combination with diamond polishing pastes of variable gradation. Appropriate selection of the grinding speed, grinding load, polishing paste and lubricant help to minimize surface damage.

The Gatan PIPS-II utilizes an Ar ion beam to sputter the TEM specimen at room temperature or at liquid nitrogen temperature (~100 K). The acceleration voltage of the ions can be varied between 0.1 kV and 8 kV. The accelerated ions hit the oscillating specimen surface at manually adjustable angles, which allows for precise control of the thinning speed and uniform removal of the sample material. Low angles in combination with low accelerating voltages and low temperatures provide gentle polishing of the electron transparent area.