pH sensing comparison of vapor and solution APTES coated Si nanograting FETs

We tested and compared the pH sensing with lithographically defined Si NGFETs modified in APTES-ethanol solution and APTES vapor. Both sensors show a good linear response over the pH range of ~ 4 - 9. The vapor APTES coated sensor exhibits higher sensitivity than the solution APTES coated sensor, although the hysteresis is slightly larger.