Rapid and Reliable Pre-Thinning to Near Electron Transparency with the Dimple Grinder II

The Model 657 Dimple Grinder II, from Gatan, is designed to rapidly remove material from a surface with minimum damage. It provides high-speed and consistent mechanical pre-thinning to near electron transparency to significantly reduce thinning and ion milling times.

Fast TEM Specimen Preparation

Mechanical grinding methods are the fastest way to reduce material thickness for specimen preparation, but they can cause unacceptable damage and may not be useful for final thinning. Nevertheless, chemical and specifically ion or fast atom methods result in limited penetration and small thin areas with relatively little damage.

The Dimple grinder can minimize the central area of a standard 100 µm thick and 3 mm diameter specimen blank to a small number of microns in just 20 minutes for silicon to 100 minutes for sapphire. Subsequently, chemical or atom beam thinning can be done quickly to create wide electron transparent areas.

Before starting the grinding process, specimens are connected to a mount with a low melting point thermoplastic polymer. The mount can also fit the model 601 TPC-tool ultrasonic cutter system and the model 623 disc grinder system, so users can safely cut the blank disc from the substrate, grind it to a thickness of nearly 80 µm, and dimpling to less than 10 µm, without dismounting the specimen.

The dimple grinder makes use of a stereo microscope to examine and align samples. So, when the microscope is set on the dimple grinder, the reflection illuminator automatically turns on, and is turned off when the transmission illuminator gets activated. A slurry cup or reservoir is supplied for using pre-mixed polishing slurries with a timer for prolonged polishing stages.

Large Transparent Areas

The dimple grinder comes with a flat wheel, used for tough specimens such as metals, and a large wheel, used for bulk specimens. Both the flat and large wheels maintain a large transparent area following processing. However, the wheels are different in both edge and shape.

The small wheel maintains a large, thick rim all-around the thin area for brittle specimens and creates sharp profiles for investigation. The spherical edges wheel allows more precise positioning of dimples and creates a spherical profile along with a small thin area. It is suitable for brittle or delicate specimens, such as semiconductors and ceramics.

Stronger Specimens

The dimpling technique creates a thin central area in the disc and leaves a solid, supporting rim that preserves the specimen from damage. For brittle specimens, a small grinding wheel with a 10 mm diameter leaves a larger rim compared to the standard wheels of 15 mm diameter.

Direct Preparation of TEM Specimens

The dimple grinder is more accurate in producing a final thickness of <3 µm and it is adequately thin for investigation in intermediate voltage TEMs. Only those materials that are resistant to mechanical damage, such as ceramics, hard metals or silicon are appropriate for such preparation. The grinding speed has to be decreased to reduce damage and the last few microns have to be removed with a particular polishing wheel in order to produce high-quality specimens.

Accurate Depth and Thickness Control

The dimple grinder features a dual measuring system consisting of an analog dial indicator that sets end stop and an electronic digital micrometer that continuously displays the dimple depth. The two indicators have a readout accuracy of 1 µm. The measuring system performs accurate dimpling without previous information of the specimen thickness.

Micro-Positioning

The dimple grinder operates on the theory of a grinding wheel rotating around a horizontal axis and a flat horizontal specimen rotating around a venial axis. Users can obtain the best results only when the two axes are at right-angles and intersect. A simple and strong alignment mechanism, integrated with the dimple grinders, helps attain this result better than ±10 µm.

Specimen Mounting Hot Plate

It is important to firmly attach specimens during dimpling, and this can be ensured by using a low melting point wax polymer to form a solid, thin and firm adhesive bond. The hot plate used for mounting a specimen is controlled thermostatically at a 130 °C mounting temperature and includes recesses to hold on to specimen mounts.

Key Features

Accurate depth and thickness control with user-defined stop point and real-time display

Direct preparation of TEM specimens to produce a final thickness of <3µm in dimpled specimens

Uses both the large wheel and flat wheel to preserve a large transparent area after processing

Micro-positioning enables both orthogonal and intersect axes for more precise positioning

Includes a thick supporting rim to preserve and strengthen the specimen after dimpling

Applications

Electronics

Material science

Natural resources

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Specifications

Specifications are subject to change.