Effects of treatment temperature on thermally‐carbonized porous silicon hygroscopicity

Abstract

Thermal carbonization of porous silicon (PSi) by acetylene has shown good stability against ageing and it also maintains a large spesific surface area of the PSi. Therefore, thermally carbonized porous silicon (TCPSi) is appropriate for humidity sensing applications. Hysteresis occurs, when water condenses into the pores of hygroscopic media, e.g. in the oxidized PSi. In the case of TCPSi, the hygroscopicity can be tuned by the treatment temperature and both a hydrophilic and hydrophobic surface can be obtained. Hysteresis can be reduced, when condesation is dimished. In this work, hygroscopicity of various PSi samples carbonized at different temperatures were studied. Contact angles and pore size distributions of differently treated samples were determined.

Porous Silicon‐Based Optical Microsensors for Volatile Organic Analytes: Effect of Surface Chemistry on Stability and Specificity

“…The ATR-FTIR spectra of the samples prepared at 485 ° C displayed more intense C-H stretches at 3055 and 2900 cm − 1 than samples prepared at 500 ° C, indicative of a greater degree of hydrophobicity that is consistent with the relative r values measured and previous studies. [ 35 ] Acetylated samples prepared at temperatures > 500 ° C appear black and lack a discernable photonic peak in the refl ectivity spectrum. Salonen and coworkers have proposed that the reaction of acetylene with porous Si at temperatures > 500 ° C could lead to significant carbonization, [ 23 ] and the black appearance is attributed to carbonaceous deposits on the porous Si surface.…”

Detecting amine vapours with thermally carbonized porous silicon gas sensor

“…This produces a hydrophobic and stable porous structure. After that, the carbonizing process was continued and the temperature was raised up to 800 ºC, producing a hydrophilic surface [8]. This two step process has been found to produce more stable and complete Si-C surface.…”

“…This method has shown its excellence, e.g., in humidity sensing applications [7]. Depending on the temperature used during the hydrocarbonization process, it is also possible to tune the hygroscopicity of the new surface inside the pores [8]. This can be utilized, for example, in PSi humidity sensors to obtain higher sensitivity with a hydrophilic surface, or in gas detection, where a hydrophobic surface reduces the effect of humidity changes during the measurement.…”

Fabrication and chemical surface modification of mesoporous silicon for biomedical applications

“…The formed surface termination contains hydrocarbons, which have similar properties as the hydrosilylated PSi [92]. The hydrocarbon-terminated surface is hydrophobic, but the contact angle can be varied by changing the treatment parameters [94], such as the duration of acetylene flow and the treatment temperature. If the treatment temperature is above 700 • C, continuous acetylene flow cannot be used.…”