Laterally Resolved Measurement of Interaction Forces between Surfaces That Are Partly Covered with Polyelectrolytes

Role of Poly(diallyldimethylammonium chloride) in Selective Polishing of Polysilicon over Silicon Dioxide and Silicon Nitride Films

“…The zeta potentials of a poly-Si film in the absence and presence of 250 ppm PDADMAC were also measured using the ZetaSpin instrument described earlier, and these results are shown in Figure . These Zp values of poly-Si are similar to those reported by several authors. − In the absence of any additive, the IEP of poly-Si is ∼3.3. However, on adding 250 ppm PDADMAC, the zeta potentials of polysilicon increased dramatically to highly positive values (≥40 mV) in the pH range 2−10, again suggesting that PDADMAC binds to and modifies the poly-Si surface.…”

“…It is also well-known that PDADMAC is a cationic polymer, which carries a large positive charge density over the entire pH range and adsorbs on different surfaces (alumina, cellulose, mica, etc. ), independent of pH. , …”

“…These Zp values of poly-Si are similar to those reported by several authors. [16][17][18] In the absence of any additive, the IEP of poly-Si is ∼3.3. However, on adding 250 ppm PDADMAC, the zeta potentials of polysilicon increased dramatically to highly positive values (g40 mV) in the pH range 2-10, again suggesting that PDADMAC binds to and modifies the poly-Si surface.…”

“…However, on adding 250 ppm PDADMAC, the zeta potentials of polysilicon increased dramatically to highly positive values (g40 mV) in the pH range 2-10, again suggesting Langmuir ARTICLE that PDADMAC binds to and modifies the poly-Si surface. Kramer et al 17 observed earlier that PDADMAC adheres to silicon surfaces. It is also well-known that PDADMAC is a cationic polymer, which carries a large positive charge density over the entire pH range and adsorbs on different surfaces (alumina, cellulose, mica, etc.…”

“…), independent of pH. 17,19 We also measured the zeta potential of a poly-Si film after polishing it with a 250 ppm PDADMAC solution at pH 10 for 1 min and subsequent cleaning with DI water adjusted to the same pH. The Zp measured in 1 mM KCl solution at pH 10, with no PDADMAC in it, is still þ45 mV, indicating that the polymer remains on the poly-Si surface after polishing and does not desorb after rinsing with water, consistent with the contact angle data described above.…”