Size Estimation of Pores on Porous Silicon by the Adsorption of Krypton and n-Butylbenzene Vapor

• Published in: Hyōmen gijutsu Vol. 46; no. 6; pp. 558 - 562
• Main Author: NONAKA, Akira
• Format: Journal Article
• Language: English
• Published: Tokyo The Surface Finishing Society of Japan 01.06.1995; Japan Science and Technology Agency
• Subjects: Butylbenzene Vapor Adsorption; Krypton Adsorption; Pore Size Estimation; Porous Silicon
• ISSN: 0915-1869; 1884-3409
• DOI: 10.4139/sfj.46.558

We estimated the size of porous silicon pores by the adsorption of krypton and n-butylbenzene vapor. Four types of samples were prepared by anodically oxidizing a single crystal p-type wafer in a solution containing hydrofluoric acid. We measured the inside pore volume, estimated from the extent of adsorption/desorption hysteresis caused by capillary condensation, and the inside surface area of pores, obtained by the difference between the total surface area including the inside pore area and the outer surface area excluding the inside pore area. The total surface area was estimated using the krypton/BET method and the outer surface area using the n-butylbenzene/gradient method. Thus, the pore size was calculated from the inside pore volume and the inside pore area estimated. Unclear beginning points of the capillary condensation were assigned in a way consistent with the Kelvin equation with the pore size estimated. We found that the relative pressure at the capillary condensation end point was fairly equal to the square root of the relative pressure at the capillary condensation start point in all samples. From the features of adsorption/desorption isotherms with hysteresis, we found the pores to be uniform in size from top to bottom and for all of the pores in a sample, the size estimated at 9.7 to 1.7nm for the samples involved.