(a) Chemical structure of ethyl-POSS bearing methacrylate monomer.
(b) Surface morphology of exposed (right part) and nonexposed (left part) areas of S2:60% TBMA 40% ethyl-POSS. The step (edge) between the two areas is clearly defined.

Thin films of ethyl polyhedral oligomeric silsesquioxane (ethyl-POSS) containing polymers at different compositions were chemically modified using laser irradiation at 157 nm. The irradiation caused photodissociation of C-O and C-H bonds followed by the formation of new chemical bonds. The content of Si-O and C-O bonds increased, as did the surface hardness. Vacuum ultraviolet (VUV) absorption, mass spectrometry, x-ray photoelectron spectroscopy, and atomic force microscopy imaging and indentation were used to evaluate the effects of the 157 nm irradiation. The chemical modification was restricted to a thin surface layer. The layer depth was determined by the penetration depth of the 157 nm VUV photons inside the thin copolymer layer. With prolonged VUV irradiation, the absorbance of the polymers increased, eventually becoming saturated. The chemical changes were accompanied by surface hardening, as evidenced by the increase in the Young's modulus from 4 to 24 GPa due to glassification of the irradiated parts. The chemically modified layer acts as a shield against photodissociation and degradation of the deeper portion of the POSS polymer by VUV radiation. Applications include the protection of solar cells on low orbit satellites from solar VUV photons.

AFM image of Thickness loss of S2:60% TBMA 40% ethyl-POSS is measured from the step (edge) between the exposed and nonexposed areas. Over a scanned distance of 32 microns, the step (etching depth) between the exposed and nonexposed areas was 15 nm for a 20 mJ/cm2 per pulse.

AFM image and high histogram of the nonexposed areas of the S2:60% TBMA 40% ethyl-POSS sample. The surface roughness histogram (z direction) is nonsymmetric around the maximum surface roughness (20 nm) and exhibits a secondary size distribution of larger size peaking at 50 nm.

AFM image of S2:60% TBMA 40% ethyl-POSS area exposed to 157 nm radiation. The surface morphology is now smoother and more symmetric with the appearance of elongated structures. The average surface roughness was 35 nm.

(a) VUV absorbance of thin films of ethyl-POSS and TBMA copolymers coated on high purity, VUV grade CaF2 substrates with different copolymer compositions (S0: 100% ethyl-POSS; S1: 40% TBMA, 60% ethyl-POSS; S2: 60% TBMA 40% ethyl-POSS; and S3: 80% TBMA, 20% ethyl-POSS). The VUV absorbance increases with increasing content of TBMA.
(b) VUV absorbance of S0 before (solid curve) and after (dashed curve) VUV irradiation at 15 mJ/cm2.

VUV transmittance of S2: 60% TBMA 40% ethyl-POSS following exposure to 157 nm. The Thickness loss of polymers can be evaluated by VUV absorption spectroscopy.

(a) Pressure gradient from dynamic out-gassing of four polymer samples.
(b) Mass spectrum of S2 exposed by 157 nm light at 0.2 mJ/cm2. The background pressure was ~10-6 mbar. In the inset, the dependence of relative intensities of the characteristic peaks at 1, 2 13, 16 and 28 amu with fluence is shown.

Left: XPS spectrum of S2 before and after 157 nm irradiation.
Right: O 1s XPS profiles of S2 before and after 157 nm irradiation.

Left: C 1s XPS profiles of S2 before and after 157 nm irradiation.
Right: XPS spectra of S2 before and after 157 nm irradiation. The Si 2p component of the nonirradiated sample at BE 98.3 eV indicates the existence of unreacted Si. VUV irradiation increases the Si–O bonding in the film.

AFM image of POSS polymer prior to irradiation indicating microfractures or microcracks (a). These were partially annealed after exposure to the 157 nm light (b).

Relevant Publications

1. Surface modification of polyhedral oligomeric silsesquioxane block copolymer films by 157 nm laser light.,
   E. Sarantopoulou, Z. Kollia, A. C. Cefalas, A. E. Siokou, P. Argitis, V. Bellas, and S. Kobe,
   J. Appl. Phys. 105 (11), art. no. 114305 (2009).
   DOI:10.1063/1.3131822
   
   
2. Effect of 193 and 157 nm laser light illumination on the surface properties of TMOS-NiCl2
   sol-gel derived material.
   L. Athanasekos, Z. Kollia, M. Vasileiadis, N. Aspiotis, D. Alexandropoulos, A. Meristoudi,
   V. Karoutsos and E. Sarantopoulou,
   J. Opt. 12, 124015 (2010).
   DOI: 10.1088/2040-8978/12/12/124015
   
   
3. Self-assembled ferromagnetic and superparamagnetic structures of Fe block copolymers hybrids.
   E. Sarantopoulou, J. Kovac, S. Pispas, S. Kobe, Z. Kollia and A.C. Cefalas,
   Superlattices Microstr. 44 (4-5), 457 (2008).
   DOI: 10.1016/j.spmi.2007.12.016
   
   
4. Dynamics and Laser Processing of Functional Fluoride Organic Surfaces at VUV Wavelengths.
   E. Sarantopoulou, Z. Kollia, M. Chatzichristidi, A. Douvas A, P. Argitis , S. Kobe and A.C. Cefalas,
   JLMN-Journal of Laser Micro/Nanoeng. 3, 24 (2008).
   
   
5. Surface modification of polymeric thin films with vacuum ultraviolet light.
   E. Sarantopoulou, J. Kovac, Z. Kollia, I. Raptis, S. Kobe and A. C. Cefalas,
   Surf. Interface Anal. 40 (3-4), 400 (2008).
   DOI: 10.1002/sia.2776
   
   

6. Nano-modification of surface morphology of Teflon AF with VUV laser light.
   E. Sarantopoulou,
   Phys. stat. sol. A 204, 1843 (2007).
   DOI: 10.1002/pssa.200675336

7. Micro/nano self-assembled 2D structures of block copolymer/Fe hybrids.
   E. Sarantopoulou, K. Gatsouli, Z. Kollia, S. Pispas, S. Kobe, and J. Kovac,
   Phys. stat. sol. A 204, 1835 (2007).
   DOI: 10.1002/pssa.200675313

8. Nano-scale spatial control over surface morphology of biocompatible fluoropolymers at 157 nm.
   E. Sarantopoulou, Z. Kollia, A.C. Cefalas, A. M. Douvas, M. Chatzichristidi, P. Argitis and S. Kobe,
   Materials Science and Engineering C, 27, 1191 (2007).
   DOI: 10.1016/j.msec.2006.09.044

9. Polymer self-assembled nano-structure and surface relief gratings induced with laser at 157nm.
   E. Sarantopoulou, Z. Kollia, A. C. Cefalas, A. M. Douvas, M. Chatzichristidi, P. Argitis and S. Kobe,
   Appl. Surf. Sci., 253, 7884 (2007).
   DOI: 10.1016/j.apsusc.2007.02.071

10. Self assembled structures on fluoro-polymers induced with laser light at 157 nm.
    Z. Kollia, E. Sarantopoulou, A.C. Cefalas, S. Kobe, P. Argitis and K. Missiakos,
    Appl. Surf, Sci. 248 (1-4), 248 (2005).
    DOI: 10.1016/j.apsusc.2005.03.043

Conference Presentations

1. Surface and chemical modification of PDMS thin films by 157 nm laser light.
   E. Sarantopoulou, Z. Kollia*, C. Riziotis and A.C. Cefalas,
   6th International Conference on Nanosciences & Nanotechnologies - NN09,
   Thessaloniki, Greece, July 13-15, 2009.

2. Surface modification properties of sol-gel and PDMS materials upon 193nm and 157 nm laser light illumination.
   E. Sarantopoulou, Z. Kollia, L. Athanasekos*, M. Vasileiadis, N. Aspiotis and D. Alexandropoulos,
   Emerging Trends & Novel Materials in Photonics, Delphi, Greece, October 7-9, 2009.

3. Self-assembled ferromagnetic and superparamagnetic structures of Fe block copolymers hybrids. (INVITED)
   E. Sarantopoulou,
   Women In Nano" Winter School. Kranjska Gora, Slovenia. 7-9 Februariou (2008).

4. Limits of hierarchical self-assembled nano/micro structures induced by vacuum ultraviolet light. (INVITED)
   A. C. Cefalas, E. Sarantopoulou, Z. Kollia and S. Kobe,
   Hot Nanotopics, Portoroz Slovenia, 23-30 May (2008).

5. Principles and methodologies of polymer nano/micro- fabrication with VUV ligth.
   E. Sarantopoulou, Z. Kollia, M. Chatzichristidi, A. Douvas, P.Argitis, S. Kobe and A.C. Cefalas.
   8th International Symposium on Laser Precision Microfabrication (2007).
   
   
6. Micro/Nano self-assembled structures of block copolymer / iron, samarium iron nanoparticles hybrid materials induced by VUV light.
   E. Sarantopoulou, K. Gatsouli, Z. Kollia, S. Pispas, S. Kobe and A. C. Cefalas.
   8th International Symposium on Laser Precision Microfabrication (2007).
   
   
7. Self -assembled magnetic structures of Fe polymers.
   E. Sarantopoulou, K. Gatsouli, Z. Kollia, S. Pispas, A. C. Cefalas, S. Kobe and J. Kovac,
   EMRS 2007, Strasburg France, May 28 - June 1, (2007).
   
   
8. Nano-depth control over self assembled structures on biocompatible polymeric thin films for bio array applications.
   E. Sarantopoulou
   TNT 2006 Grenoble France, 4-8 September (2006).
   
   
9. Polymer self-assembly with lasers at 157 nm.
   E. Sarantopoulou, Z. Kollia, A. C. Cefalas , A. M. Douvas, M. Chatzichristidi, P. Argitis and S. Kobe,
   EMRS 2006, Nice France, 29 May-2 June (2006).
   
   
10. Self assemply of fluor and other polymers with laser light at 157 nm.
    Z. Kollia, E. Sarantopoulou, A. C. Cefalas and S. Kobe,
    EMRS 2004, G-Current trends in nanoscience-from materials to applications,
    Strasbourg France, May 24-28 (2004).
    
    
11. Self-assempled structures induced with laser light at 157 nm.
    Z. Kollia, E. Sarantopoulou, A. C. Cefalas, S. Kobe, P. Argitis and K. Missiakos,
    4th International conference on photo excited processes and applications, ICPEPA, Lecce Italy, 5-14 September (2004).