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“The concentration of the PVAm-1595 solution is diminishing slightly because of the HCl addition during the pH adjusting process. Table 2. Layer Thicknesses of Spin-Coated PVAm-1595 Films on Cu—Si Wafers after Their Curing and Extraction ir Water as a Function of the pH of the Polymer Solution

Table 2 “The concentration of the PVAm-1595 solution is diminishing slightly because of the HCl addition during the pH adjusting process. Table 2. Layer Thicknesses of Spin-Coated PVAm-1595 Films on Cu—Si Wafers after Their Curing and Extraction ir Water as a Function of the pH of the Polymer Solution

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Figure 2. XPS wide-scan and high-resolution spectra of copper metal particles coated with PVAm-9095 at pH 8 under an argon atmosphere. The insets show the high-resolution (b) C 1s, (c) N 1s, and (d) Cu 2p element spectra. XPS was employed to characterize the polymer-modified copper metal particles. The XPS method is a surface-sensitive spectroscopic technique analyzing a sample surface composi- tion in a depth not greater than 8 nm. As an example, Figure 2
Figure 2. XPS wide-scan and high-resolution spectra of copper metal particles coated with PVAm-9095 at pH 8 under an argon atmosphere. The insets show the high-resolution (b) C 1s, (c) N 1s, and (d) Cu 2p element spectra. XPS was employed to characterize the polymer-modified copper metal particles. The XPS method is a surface-sensitive spectroscopic technique analyzing a sample surface composi- tion in a depth not greater than 8 nm. As an example, Figure 2
“R represents the backbone of the PVAm polymer. Scheme 1. Mechanism Illustrating the Spontaneous Linkage of PVAm to the Copper Surfaces during the Drying Process of the PVAm/Copper Adsorbates*
“R represents the backbone of the PVAm polymer. Scheme 1. Mechanism Illustrating the Spontaneous Linkage of PVAm to the Copper Surfaces during the Drying Process of the PVAm/Copper Adsorbates*
“All elemental ratios were determined on carefully dried samples employing XPS. >The DH values describe a fraction of the formamide groups of the PVFA prepolymer that were converted into primary amino groups by basic hydrolyzation. “pH of the aqueous polyelectrolyte solution during the adsorption process. #Values were not determined. “For comparison, values from ref 25 are given in Table 1.
“All elemental ratios were determined on carefully dried samples employing XPS. >The DH values describe a fraction of the formamide groups of the PVFA prepolymer that were converted into primary amino groups by basic hydrolyzation. “pH of the aqueous polyelectrolyte solution during the adsorption process. #Values were not determined. “For comparison, values from ref 25 are given in Table 1.
Figure 3. UV/vis absorption spectra and visual impression of the separated aqueous solution of the PVAm-9095 copper mixture after an adsorption time of 10 min. The adsorption processes were carried out under ambient conditions at pH S (a), pH 8 (b), and pH 11 (c). The two component peaks H and H’ in the high-resolution Cu 2p XPS spectrum (Figure 2d), the DRIFT spectra (Figure S1), and the visually observed dark-brown discoloration of the substrate surfaces (Figure S2) confirmed the formation of oxide layers on the copper metal surfaces. The formation of copper oxide species on the copper metal surface also seems to be important for the dissolution process of copper ions by their interaction with adsorbed PVAm copolymers. This assumption was supported by the following studies. During the adsorption of the PVAm-9095 copolymer under ambient conditions, the supernatant solution was slightly blue (photograph in Figure 3)
Figure 3. UV/vis absorption spectra and visual impression of the separated aqueous solution of the PVAm-9095 copper mixture after an adsorption time of 10 min. The adsorption processes were carried out under ambient conditions at pH S (a), pH 8 (b), and pH 11 (c). The two component peaks H and H’ in the high-resolution Cu 2p XPS spectrum (Figure 2d), the DRIFT spectra (Figure S1), and the visually observed dark-brown discoloration of the substrate surfaces (Figure S2) confirmed the formation of oxide layers on the copper metal surfaces. The formation of copper oxide species on the copper metal surface also seems to be important for the dissolution process of copper ions by their interaction with adsorbed PVAm copolymers. This assumption was supported by the following studies. During the adsorption of the PVAm-9095 copolymer under ambient conditions, the supernatant solution was slightly blue (photograph in Figure 3)
Scheme 2. Dissolution of Cu** Ions and Their Complex Formation with PVAm Copolymer Chains* “The bridging effect of dissolved and complexed Cu™* ions enhances the amount of adsorbed PVAm on the copper metal surface.
Scheme 2. Dissolution of Cu** Ions and Their Complex Formation with PVAm Copolymer Chains* “The bridging effect of dissolved and complexed Cu™* ions enhances the amount of adsorbed PVAm on the copper metal surface.
The average polymer layer thicknesses were determined by ellipsometric measurements (Figure 5). When concentrations Figure 5. Layer thicknesses of spin-coated PVAm-1595 films on Cu— Si wafers after curing and extraction as a function of polymer concentration. The pH of the aqueous PVAm-1595 solutions was 10.6.
The average polymer layer thicknesses were determined by ellipsometric measurements (Figure 5). When concentrations Figure 5. Layer thicknesses of spin-coated PVAm-1595 films on Cu— Si wafers after curing and extraction as a function of polymer concentration. The pH of the aqueous PVAm-1595 solutions was 10.6.
As it can be seen from the AFM image in Figure 4a,b, the Cu-—Si substrate shows a closed, uniform copper layer. After the Figure 4. (a, c) AFM height and (b, d) phase images (2 zm X 2 um) of (a, b) a copper-coated silica wafer Cu—Si and (c, d) the Cu—Si sample spin coated with a 2 wt % PVAm-1595 solution at pH 10.6, which was subsequently cured at 120 °C. (e) Height profiles of the regions marked in image c. The thickness of the polymer layer was about 50 nm.
As it can be seen from the AFM image in Figure 4a,b, the Cu-—Si substrate shows a closed, uniform copper layer. After the Figure 4. (a, c) AFM height and (b, d) phase images (2 zm X 2 um) of (a, b) a copper-coated silica wafer Cu—Si and (c, d) the Cu—Si sample spin coated with a 2 wt % PVAm-1595 solution at pH 10.6, which was subsequently cured at 120 °C. (e) Height profiles of the regions marked in image c. The thickness of the polymer layer was about 50 nm.
An experimental series with alternating tempering and extraction steps was carried out to prove the swelling behavior of the thick PVAm films produced from PVAm-1595 solutions at pH 10.6. The layers were extracted directly after the curing process. The highly polar PVFA-co-PVAm copolymer layer incorporated water molecules during extraction. The thickness of those swollen PVFA-co-PVAm layers is again slightly increased as shown in Table 2 and Figure 6. A subsequent Scheme 3. Assumed Conformation of PVAm Molecules as a Function of the pH of the Surrounding Medium
An experimental series with alternating tempering and extraction steps was carried out to prove the swelling behavior of the thick PVAm films produced from PVAm-1595 solutions at pH 10.6. The layers were extracted directly after the curing process. The highly polar PVFA-co-PVAm copolymer layer incorporated water molecules during extraction. The thickness of those swollen PVFA-co-PVAm layers is again slightly increased as shown in Table 2 and Figure 6. A subsequent Scheme 3. Assumed Conformation of PVAm Molecules as a Function of the pH of the Surrounding Medium
Figure 6. Investigation of the stability of a PVAm-1595 film by extraction/curing cycles. The polymer film was applied from a 2 wt % aqueous PVAm-1595 solution (pH 10.6) on Cu—Si. The PVAm-1595 layer thickness increases in the presence of the extraction solvent. After curing (via the drying process), the PVAm-1595 appeared to be reconstructed. Only long extraction times slightly decrease the applied polymer layer. (A) After 16 h of tempering at 120 °C, (B) + 16h of extraction with H,O, (C) + 20 min of tempering at 100 °C, (D) + 17 h of extraction with H,O, (E) + 90 min of tempering at 100 °C, (F) + 65 h of extraction with ethanol, (G) + 90 min of tempering at 100 °C.
Figure 6. Investigation of the stability of a PVAm-1595 film by extraction/curing cycles. The polymer film was applied from a 2 wt % aqueous PVAm-1595 solution (pH 10.6) on Cu—Si. The PVAm-1595 layer thickness increases in the presence of the extraction solvent. After curing (via the drying process), the PVAm-1595 appeared to be reconstructed. Only long extraction times slightly decrease the applied polymer layer. (A) After 16 h of tempering at 120 °C, (B) + 16h of extraction with H,O, (C) + 20 min of tempering at 100 °C, (D) + 17 h of extraction with H,O, (E) + 90 min of tempering at 100 °C, (F) + 65 h of extraction with ethanol, (G) + 90 min of tempering at 100 °C.
“The concentrations of the spin-coating solutions were 1 wt % (A—E) and 2 wt % (F) as references. The information depth of the XPS method is not more than 8 nm for take-off = 0°, 4 nm for take-off = 60°, and 2 nm for take-off = 75°. (A) PVAm-1595/Cu-—Si, not cured, stored for 4 weeks at room temperature; (B) PVAm-1595/Cu-Si, not cured, measured immediately after spin coating; (C) PVAm-1595/ Cu-Si, cured for 16 h at 120 °C; (D) PVAm1595/Cu-—Si, cured for 16 h at 120 °C, extracted with water for 16 h; (E, F) PVAm-1595/ Cu-—Si, cured for 16 h at 120 °C, extracted with water for 16 h and dried for 90 min at 100 °C. Table 3. Angle-Resolved XPS Studies to Quantify the Amounts of Nitrogen and Copper in the Surface Regions of PVAm-1595-Coated Cu—Si Wafers*
“The concentrations of the spin-coating solutions were 1 wt % (A—E) and 2 wt % (F) as references. The information depth of the XPS method is not more than 8 nm for take-off = 0°, 4 nm for take-off = 60°, and 2 nm for take-off = 75°. (A) PVAm-1595/Cu-—Si, not cured, stored for 4 weeks at room temperature; (B) PVAm-1595/Cu-Si, not cured, measured immediately after spin coating; (C) PVAm-1595/ Cu-Si, cured for 16 h at 120 °C; (D) PVAm1595/Cu-—Si, cured for 16 h at 120 °C, extracted with water for 16 h; (E, F) PVAm-1595/ Cu-—Si, cured for 16 h at 120 °C, extracted with water for 16 h and dried for 90 min at 100 °C. Table 3. Angle-Resolved XPS Studies to Quantify the Amounts of Nitrogen and Copper in the Surface Regions of PVAm-1595-Coated Cu—Si Wafers*
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