PC4250 Introduction to Surface Analysis Techniques

References for Surface Science Main text: Vickerman (ed) Surface Analysis, Wiley 1997 Further Reading: Woodruff & Delchar, Modern Techniques of Surface Science, CUP 1986 Wiesendanger, Scanning Probe Microscopy and Spectroscopy, CUP 1994 On-line resources:

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Surface Science Lab NUS UHV systems: VG ESCA MkII/SIMSLAB Cameca IMS 6f Magnetic sector SIMS) VT-STM/XPS/LEED system + growth chamber with molecular beam & reactive atom sources [+ cryogenic STM] Soft X-ray synchrotron end station on SINS beamline [+ growth chamber + STM/AFM] [EXAFS endstation]

Surface Techniques Most physics techniques can be classified as scattering experiments: a particle is incident on the sample, and another particle (not necessarily the same) is detected after the interaction with the sample. Surface Physics is no exception: we can think of an incident Probe X and a Response Y. If we understand the nature/physics of the scattering, then we can interpret the experiment and deduce the corresponding characteristics of the sample. Probe X Response Y Electrons (E 0,k 0,..spin s)Electrons (E,k,..spin s) Radiation (  0,k 0,..polarisation) Sample Radiation ( ,k,..polarisation) Atoms (E 0,k 0,Z)Atoms (E,k, Z') Ions (E 0,k 0,  Z)Ions (E,k,  Z')

Overview of techniques

Reasons for surface sensitivity The incident particle or the probe particle has a short mean free path,. –XPS - emerging electrons in the energy range eV have for inelastic scattering in solids, of order 1 nm or less. –LEED - both the incident and the emergent electrons have short mean free paths for energy loss processes –SIMS - emergent ions have a very high probability of being neutralised if they do not originate very near the surface. The sample has a large surface to volume ratio. –allows us to extract surface information from techniques which are not particularly surface sensitive. –use powdered/exfoliated samples and perform heat capacity or other thermodynamic measurements, X-ray or neutron scattering –use thin film samples and concentrate on the surface-related contribution; e.g. TEM done on thin films around nm thick.

Primary Particle Probes