Wang et al. Nanoscale Research Letters 2011, 6:483 http://www.nanoscalereslett.com/content/6/1/483 Page 3 of 5 Figure 1 A strategy schema and designed molecule. (R = Cl; R’ = NH2(CH2)3; R” = CH2CH3; Rx = NH (CH2)3). to yield TESPA. Yield was 75.6%, and m.p. > 203°C. Ele- mental analysis calculation for C12H23N4S2O3NaSi was: C, 37.29%; H, 6.00%; N, 14.49%; however, found was: C, 37.46%; H, 6.03%; and N, 14.44%. The results of NMR, FT-IR, and MS also suggest that TESPA have been synthesized (see Additional file 1). The XPS spectra of untreated and TESPA-treated epoxy resin substrate are shown in Figure 2. It can be seen that only the peaks of C1s, O1s, and N1s are observed for the untreated substrate, while the peaks of N1s, S2s, S2p, Si2s, and Si2p corresponding to the TESPA SAM-covered substrate. The results confirmed the formation of the TESPA SAM on the epoxy resin substrate. It can be concluded that the Si-OH groups of hydrolyzed TESPA (see Figure 1) react with the polar groups on the pre-treated epoxy resin surface to form the TESPA SAM. The thickness of the TESPA SAM was about 2.8 nm. The results of XPS for the TESPA SAM before and after Pd catalyzation are shown in Figure 3. The pre- sence of Sn3p, Sn3d, Pd3s, Pd3p, and Pd3d peaks sug- gests the adsorption of catalyst to TESPA SAM-coated surface, and the designed TESPA molecule covalently binds colloidal PdII catalysts, which can promote ELD copper film onto the TESPA SAM-coated surface [22]. The surface image of TESPA SAM-coated epoxy resin substrate after ELD copper is shown in Figure 4. It can be seen that the surface is uniform and compact. The adhesion strength between TESPA SAM-coated epoxy resin and ELD copper film was up to 13.8 MPa, which could satisfy the purpose of TESPA SAM as adhesion enhancer and diffusion barrier layer, while the adhesion strength between non-TESPA-treated substrate and ELD copper film was only 1.2 MPa. It is clearly indicated that the TESPA SAM can be applied as interfacial adhesion enhancer and diffusion barrier. It is expected that Figure 2 XPS survey spectra of epoxy resin surface: (a) uncoated and (b) TESPA SAM-coated. X-ray source is monochromated Al Ka ray. Testing area is 800 × 2,000 μm. Takeoff angle is 45°. The pressure in the preparation chamber is less than 10-7 Torr and less than 4 × 10-10 Torr in the analysis chamber. Figure 3 XPS survey spectra of TESPA SAM-coated epoxy resin surface. (a) Before Pd catalyzation and (b) after Pd catalyzation.