"God made the bulk; the surface was invented by the devil."- Wolfgang Pauli This quote represents the challenges in understanding surface phenomena, due to the anisotropic environment of surface atoms. These challenges become even bigger for thin film, since the atoms are neighbored by different environments for the top and bottom sides, along with additional layers formed called interfacial layers. These days, the importance of surface and thin film technologies are rapidly growing in high-tech industries: semiconductor, display, LED, photovoltaic, et cetera. More than one hundred analysis techniques have been developed and released so far, and even more are under development.
TEM allows direct imaging of the atomic structure of materials, while EDS/EELS provides elemental composition information. Therefore, TEM & EDS/EELS are very powerful tools which study both films and interfaces. In addition to the regular HR-TEM, Outermost Technology also provides services using Cs (Aberration) - corrected TEM, which generates 5x better resolution than HR-TEM
SIMS is a technique used to analyze the composition of solid surfaces and thin films via sputtering-off the specimen with a focused ion beam, then collecting and analyzing ejected secondary ions through their mass/charge ratios. Due to its high sensitivity, SIMS is mainly used to analyze trace level elements such as doping levels in semiconductor, LED, and other industries.
XPS is a surface-sensitive quantitative spectroscopic technique which measures the elemental composition down to 0.1% range along with empirical formula, chemical state and electronic state of the elements within the material. d-XPS is XPS coupled with surface etching by a high energy ion beam, which is used to study the compositional and chemical change of a material along the film depth.
Auger electron spectroscopy is a common analytical technique used specifically in the study of surface of a material. This technique utilizes the 'Auger effect', discovered in the 1920s. It is more surface sentitive than XPS since it uses electrons instead of photons for detection. d-AES is AES coupled with high energy ion beam to study the compositional change along the depth.
FIB is a technique used particularly in the semiconductor industry. FIB utilizes a focused ion beam (typically Ga+), which causes surface sputtering that generates neutrals, ions, and electrons. Its detector then analyzes the information from the secondary particles for patterned structure imaging and compositional mapping.
SEM is a type of electron microscope which produces images of a sample by scanning the surface with a focused electron beam, which interacts with atoms in the sample, producing various signals that contain information about the sample's surface topography and composition. SEM can achieve typical resolution of 1nm.
AFM is a type of scanning probe microscopy (SPM), with demonstrated resolution on the order of fractions of a nanometer, which is more than 1000 times better than the optical diffraction limit. It utilizes piezoelectric control for locating and scanning, and uses van der Walls force interaction between sample surface and scanning tip for detection. Typical analysis range is from 0.01um2 to 10,000um2.
SE is an optical technique for investigating the dielectric properties (complex refractive index or dielectric function) of thin films. SE measures the change of polarization upon reflection or transmission and compares it to a model. It can also characterize composition, roughness, thickness (depth), crystalline nature, and electrical conductivity, which requires trained modeling for measured signal interpretation.