Printer Friendly- Faculty Advisor: C.Sung
- Supervisor: M.J. Downey
Scanning Probe Microscopy - APM
Nondestructive methods for determining topographic and structural information on a submicron scale of solid surfaces: metals, semiconductors and insulators
Scanning Tunneling Microscopy (STM) Atomic Force Microscopy (AFM)
Instruments: Park Scientific Instruments SFM-BD2 and STM-SA1
Features : The APM techniques include STM & AFM and are capable of characterizing the surface condition, on an atomic-to-micron scale, of a wide range of solid samples that include crystalline surfaces (conducting and insulating), polymers, biomolecules, semiconductor devices and components. The movement of the sample is accomplished by a programmed, high precision piezoelectric scanning assembly and measurements are carried out under ambient or vacuum conditions. Physical and chemical properties of surfaces can be measured with high spatial and height resolution in the range of 1 nm and can be displayed in a 3-dimensional presentation. Ultra-high resolution imaging of single atoms, molecules and surface defects on are easily imaged. In addition, a DekTak IIA, with a 12 µm diameter stylus, is also available for measuring film thicknesses, step heights and crater dimensions as a result of depth profiling or milling.
Applications:
- Atomic level structures of crystalline materials
- Molecular resolution in biomolecules, liquid crystals, and polymers
- Characterization of surface roughness
- Electronic structure of materials
- Magnetic imaging of surface
Features: This is a software program that allows for the processing of images obtained by optical microscopy, SEM, TEM, and STM/AFM. The mage processing capability includes a fast Fourier image enhancement and real color analysis. Quantitative results and correlation of the morphological features of images are performed.
Applications:
- Quantitative determination of grain size, shape, and boundary areas per unit volume in crystalline materials.
- Quantitative determination of second phase volume fractions, sizes, interfacial areas per unit volume, and spacings.
- Quantitative determination of particle size and shape distribution in powders.
- Quantitative determination of aspect ratios of fibers in composites.
- Faculty Advisor: Mike Downey
Structure and compound identification of single phase and multiphase crystalline materials from intensity versus angle of diffraction scans. Broadening due to crystal size and defects may be studied. In polymer samples, the degree of crystallinity and preferred orientation may be assessed.
Instruments: Philips Diffractometors/Rigaku RU-300E Diffractometer
Features: The XRD laboratory consists of several Philips generators and with vertical diffracted beam monochromators. In addition, a state-of -the-art, computer controlled Rigaku 18KW rotating anode generator coupled to a horizontal diffractometer with a curved crystal monochromator and parallel beam optics is available. This permits insitu studies at elevated temperatures, residual stress measurements on flat or curved surfaces, the determination of the amorphous phase content in a crystalline matrix, glancing angle thin film studies. and precision lattice parameter measurements. An array of cameras are available for polycrystalline and single crystal studies. with sample spinning accessories and an array of camera attachments (Debye-Scherrer, Gandolfi, Guinier, and Laue cameras) for performing phase characterization of small samples. Detection sensitivity is in the range of 2 % for light element matrices. In addition, for special structure analyses a high x-ray intensity rotating anode x-ray diffractometer can be applied in the analysis of metals, ceramics, powders and semiconductors. A fully computerized data collection system coupled with search capabilities and the JCPDS-ICDD diffraction database allows for automated phase identification. Other accessories include a high temperature stage (1400 degrees C) for measuring thermal expansion coefficients and phase transformations as a function of temperature. Stress analysis and glancing angle diffraction from near-surface region of solid samples can be carried out as well as the utilization of the Rietveld refinement process for determining the structure of unknown materials.
Applications:
- Identification of compounds in crystalline materials.
- Quantitative phase analysis
- Crystal structure and precision lattice parameter measurements
- Determination of orientation of crystal axis
Analytical Electron Microscopy - AEM
Microcharacterization of materials for structure, crystallinity and chemical information
Instrument: Philips EM-400
Features: The electron microscope is a versatile instrument which includes numerous capabilities: Electron Energy Loss Spectrometry (EELS), Convergent Beam Electron Diffraction (CBED), Transmission Electron Microscopy (TEM), Scanning TEM (STEM), Energy Dispersive X-ray Spectrometry (EDXS), Scanning Electron Microscopy (SEM). Facilities for specimen preparation include argon ion etching, sample dimpling, polishing and coating are readily available. The technique is capable of imaging the internal microstructure of materials in the range of 1,000x to 500,000x. Elemental analysis of microstructural features or regions as small as 10 nm can be determined qualitatively or semiquantitatively. Crystal structure, phase identification, and crystal orientation can be determined on a nanometer scale and, with the use of special temperature controlled sample stage, TEM can be carried out as a function of temperature.
Applications:
- Complete description of the internal microstructure of metals, ceramics, semiconductors, polymers, biomaterials, composites, etc.
- High resolution imaging to observe atomic structure.
- Complete crystallographic analysis using CBED Composition and chemical state from microareas using EDXS and EELS.
- BSE and SE imaging in STEM mode
- ALCHEMI technique
Scanning Electron Microscopy/Electron Probe Microanalyzer - SEM/EPMA
High magnification, high resolution, high depth of field microscope for characterizing the topography and composition of solid surfaces: metals, semiconductors, insulators and polymers
Instrument: Amray 1400
Features: The SEM extends the range of optical microscopes to higher magnifications (of 50,000x) with the advantage of increased depth resolution. The cathode is a high brightness LaB6 electron source yielding improved spatial resolution and increased detection limits. A wavelength dispersive analyzer (WDA) allows for the measurements of light elements such as C, N, O, & F. Detection limits are typically in the ppm range. The instrument can be used for voltage contrast studies and EBIC; and for producing secondary and backscattered electron images and chemical mapping of specimen surfaces. The instrument is ion pumped thereby reducing any untowards surface effects sometimes associated with diffusion pumped vacuum systems. Qualitative and semiquantitative elemental analyses can be conducted on samples in as small as <0.1 mm diameter. Fractured samples can be imaged for topographic and microstructural information revealing the nature of the internal structures of the sample. Facilities for sample preparation such as potting, polishing and coating are readily available.
Applications:
- Fracture surface and failure analysis
- Phase and inclusion identification in metals, ceramics, composites, and minerals
- Phase distributions and volume fraction analysis
- Semiconductor device failure analysis
- Stereographic image pairs for 3-D viewing
Rutherford Backscattering Spectrometry - RBS
- Faculty Advisor: G. Kegel (Department of Physics and Applied Physics)
Composition of surfaces and multilayer thin films, nondestructively
Instrument: 5 MeV Van der Graff
Features: The instrument is capable of producing a high energy beam of protons (H+), H+2 or alpha particles (He+2) depending upon the particular problem. The helium beam provides superior depth resolution at a reduced sampling depth. The hydrogen beam has an increased sampling depth with reduced depth resolution and may be limited because of the formation of (nuclear) reaction byproducts particularly for the low Z elements. A computer program is available for simulating or modeling the RBS spectrum of the sample, prior to, and after the RBS analysis.
Applications:
- Ion implanted depth profiles
- Elemental composition of multilayer thin films
- Composition and thickness of interfacial regions