Abstract

Time of Flight Secondary Ion Mass Spectrometry (TOF-SIMS) is a highly sensitive surface analysis technology. By stimulating the sample surface with primary ions, extremely small amounts of secondary ions are produced; and then the mass of ions can be measured through the time they fly to the detector for different masses. At present, this measurement method with high resolution has been widely used in physics, chemistry, microelectronics, biology, pharmacy, space analysis, and other industrial and research fields (Belu et al., 2003).

Time of Flight Secondary Ion Mass Spectrometry (TOF-SIMS)

Figure 1: CAMECA IMS3f (1980) Magnetic SIMS Instrument (Photo by CAMECA Archives licensed under CC-BY-SA 3.0)

When the sample's surface is bombarded by high-energy focused primary ions, these ions are injected into the target sample, and then the kinetic energy can be transferred to the solid atoms. Neutral particles and positively and negatively charged secondary ions are sputtered through the stacking collision, and thus the surface and internal element distribution characteristics of the bombarded sample can be analyzed according to the mass signal of the sputtered secondary ions.

Notes : Sputtering occurs when the below condition is reached.

After a series of double-body collisions under the action of high-energy primary ions, the bounced lattice atoms within the sample reaching or near the surface acquire the energy and orientation required to escape the solid.

The main functions of the TOF-SIMS method

1. Identification of inorganic or organic layers on metal, glass, ceramic, film or powder surfaces;

2. Determination of concentration distribution of oxide surface layer, corrosion film, leaching layer and diffusion layer along depth;

3. Determination of identification of concentration distribution along depth of trace dopants (≤ 1000 ppm) diffused or ion-implanted into semiconductor materials;

4. Determination of hydrogen concentration and hydrogen distribution along depth in embrittled metal alloys, vapor-deposited films, hydrated glasses and minerals;

5. Quantitative analysis of trace elements in solids;

6. Analysis of isotopic abundance in geological samples and silver-bearing samples;

7. Tracer studies with isotopically enriched materials (e.g., studies of diffusion and oxidation)

8. Identification of phase distribution in minerals, multiphase ceramics and metals;

9. Identification of secondary phase distribution caused by grain boundary segregation, internal oxidation or precipitation

Sample preparation requirements and precautions

1. The maximum size of the sample is 1×1×0.5 cm; it needs to be cut if the size is too large;

2. Hands and sampling tools should not touch the tested location; vacuum packaging or other packaging that can isolate the external environment should be used to avoid external contamination;

3. TOF-SIMS test samples are not limited by electrical conductivity;

4. The element analysis range of TOF-SIMS is H-U, including elements and molecular states of organic and inorganic materials, and the detection limit is ppm.

References