1. The Surface Analysis Laboratory Cutting and Sputtering: Getting to the Buried Interface John F Watts The Surface Analysis Laboratory Department of Mechanical Engineering Sciences 2 July 2014

2. The Surface Analysis Laboratory The Problem!

3. The Surface Analysis Laboratory Inorganic Layers J E Castle et al, Corr Sci, 16, 145-158, (1975)

4. The Surface Analysis Laboratory High Temperature Oxidation J C Rivière et al, Surf Sci, 117, 629, (1982) R K Wild, Spectrochim Acta, 40B, 827, (1985)

5. The Surface Analysis Laboratory d Interface Region Substrate Adhesive or Coating 10’s  m - mm 100’s  m - mm  ARXPS d ~10nm  X-ray spectroscopies d ~200nm  RBS d ~1μm Buried Interfaces: The Problem One solution is mechanical sectioning of the sample followed by analysis of the exposed interfacial region

6. The Surface Analysis Laboratory The Buried Interface Obtaining analytical information from intact interfaces is very difficult. Carrying out in-situ experiments within the spectrometer can be useful but only rarely is the interphase chemistry exposed in this manner J F Watts, Surf Interf Anal, 12, 497-503, (1988)

7. The Surface Analysis Laboratory Oxide Stripping Chemical removal of metal substrate, depth profiling of oxide in situ by ion sputtering. Interphase can then be analysed directly J F Watts, J E Castle, J Mat Sci, 18, 2987, (1983)

8. The Surface Analysis Laboratory XPS Spectrum at Interphase Iron 2p3/2 spectrum showing Fe(II) component at interface. Oxide is entirely Fe(III). Fe(II) satellite Fe(II)

9. The Surface Analysis Laboratory Model of Interphase

10. The Surface Analysis Laboratory Complementary Dissolution

11. The Surface Analysis Laboratory Energy Filtered TEM (a) (b) Energy-filtered (PEELS) TEM images of adhesively bonded aluminium showing the interpenetration of organic and oxide phase that is achieved when a primer is used (a). In the absence of a primer (b) the adhesive merely forms a interfacial boundary with the oxide. A J Kinloch, M Little, J F Watts, Acta Materialia, 48, 4543, (2000)

12. The Surface Analysis Laboratory MICROM 355S

13. The Surface Analysis Laboratory Ultra-Low Angle Microtomy angled sectioning block sample polyethylene Angle Sectioning Block 12 x 12 x 7 mm 3 + 25  m = 0.03 O + 50  m = 0.07 O + 100  m = 0.15 O + 200  m = 0.33 O microtome blade

14. The Surface Analysis Laboratory ULAM Depth Profiling Coating Small area XPS analysis mode (100  m) Substrate  XPS spot size/  m ULAM taper angle/ o 0.030.332.0 100606003500 1513100500 Depth Resolution ULAM/nm S J Hinder, C Lowe, J T Maxted, J F Watts, J Mater Sci, 40, 285, (2005)

15. The Surface Analysis Laboratory PVdF (topcoat) Polyurethane (primer) ULAM/Small Area XPS Depth Profile S J Hinder, J F Watts, Surf Interf Anal, 36, 1032-1036, (2004).

16. The Surface Analysis Laboratory ToF-SIMS of ULAM Interface d) b)a) c) 1 3 2 +ve SIMS -ve SIMS Polyurethane ions PVdF ions (a)m/z = 149: C 8 H 5 O 3 + (b)m./z = 26: CN - (c)m/z = 59: C 3 H 4 F + (d)m/z = 19: F - 500  m 250 nm S J Hinder, C Lowe, J T Maxted, J F Watts, Surf Interf Anal, 36, 1575, (2005)

17. The Surface Analysis Laboratory a) 25 41-42 49 66 100 121 c) 19 49 39 85 Point 2: Bulk Polyurethane Point 1: Bulk PVdF c) 1 3 2 Negative SIMS Spectra from Images

18. The Surface Analysis Laboratory b) 19 31 55 71 87 85 121 185 141 Point 3: PU and PVdF at Interface c) 1 3 2 Reconstructed ToF-SIMS of Interphase

19. The Surface Analysis Laboratory 31 55 71 85 185 41 A negative ion ToF-SIMS mass spectra of the pure acrylic co-resin component of the PVdF topcoat formulation in the mass range 30-200u  x10 ToF-SIMS of Acrylic Copolymer Component of PVdF Topcoat

20. The Surface Analysis Laboratory a)b) e)f) d)c) Negative Ion Mass Selected Images (a)m/z = 31: CH 3 O - (b)m/z = 55: C 3 H 3 O - (c)m/z = 71: C 3 H 3 O 2 - (d)m/z = 85: C 4 H 5 O 2 - (e)m/z = 87: C 4 H 7 O 2 - (f)m/z = 141: C 9 H 13 O 4 - Retrospective Images of Acrylic Ions

21. The Surface Analysis Laboratory Model Specimen for ULAM Adhesive Aluminium foil Adhesive Line scan used Interface Adhesive/Aluminium/Adhesive Adhesive M-L Abel, unpublished data (2008)

22. The Surface Analysis Laboratory Polyamide Powder Coating + Aminosilane addition ULAM is carried out on the intact outer surface to provide profile of air/coating interface and delaminated coating interfacial failure surface to provide steel/coating profile 100 mm thick thermoplastic polyamide powder coating with aminosilane added to the powder stock prior to spray coating M Guichenuy, J F Watts, M-L Abel, M Audenaert, Surf Interf Anal, 38, 168-171, (2006).

23. The Surface Analysis Laboratory Aminosilane in PA11 Coating // Air/Coating InterfaceCoating/Steel Interface 0 1 3 4 2 Atomic % Depth / μm 100  m thick polyamide powder coating with aminosilane added to the powder stock prior to spray coating

24. The Surface Analysis Laboratory d Interface Region Substrate Adhesive or Coating 10’s  m - mm 100’s  m - mm Deposit a very thin layer of organic phase This may be from the plateau region of an adsorption isotherm Thin Film Solution Prepare specimen at monolayer coverage (i.e. plateau region) for XPS or ToF-SIMS analysis It is then possible to probe interface chemistry directly

25. The Surface Analysis Laboratory Organosilane Adhesion Promoters Molecular Dynamics Models of: (a)Epoxy (b)Amino (c)Vinyl

26. The Surface Analysis Laboratory ToF-SIMS to Identify Specific Interactions The intense SiOAl + peak is indicative of a covalent bond between the aluminium oxide and the organosilane adhesion promoter

27. The Surface Analysis Laboratory Conclusions  A variety of “mechanical” and chemical methods to approach interfaces  ULAM provides an easy way to section samples at very low angles which has the potential to provide chemical depth profiles at very high depth resolution when used in conjunction with a surface analysis method such as XPS or ToF- SIMS  Polymer/polymer systems are straightforward, if the candidate substrate is metal a thin foil must be used  Thermosetting systems can be cut at ambient temperature, thermoplastic systems may need a cold stage