Study On Preparation And Humidity Sensing Performance Of Ordered Porous Silicon

Porous silicon is a new type of inorganic functional nano-material with unique structure and excellent properties.It is widely used in photoelectric device,microelectronic system,biomedicine and sensing fields.However,porous silicon prepared through traditional etching process still exists many disadvantages,such as mixed and disorderly channel,uncontrolled pore size and etc.In recent years,preparation of ordered porous silicon with neat channel,uniform and adjustable pore size and diverse morphologies is the hot topic,which can enrich porous silicon's morphology and structure and wildly broaden its application areas.In this paper,two kinds of porous silicons with different micromorphologies and pore structures were successfully prepared through low-temperatured magnesiothermic reduction of mesoporous silica sieves.The crystalline structure,morphology and pore structure of porous silicon were characterized.Then,the products were made into sensors through a facial drop-coating method to evaluate their sensing properties to humidity.The main research achievements and results are as follows:(1)The experiment parameters were optimized through a series of experimental studies.Then using magnesium as a reducing agent,the MCM-41 silica mesoporous molecular sieve with neat one-dimensional channel structure were reduced to porous silicon(Si-MCM-41)with a appropriate mole ratio(1:2.5)of reactants at low temperature(650?).The results showed that the amorphous silica were converted into the crystalline silicon by the magnesiothermic reduction.To a large extent the product inherited the original template's morphology,and possessed a similar regular pore structure and uniform pore size,compared with the original template,its structure is relatively loose,porous silicon has a higher porosity.(2)Under the same experimental conditions,porous silicon(Si-SBA-15)was successfully converted from SBA-15 silica mesoporous molecular sieve with two-dimensional channel structure by a magnesiothermic reduction.The product retained awormlike morphology similar to that of the original template,and owned a similar regular pore structure and uniform pore size.(3)Two kinds of porous silicons product with different morphology were used into sensing element to study humidity sensing performance,respectively.The results indicated that two kinds of porous silicon materials have high sensitive characteristic for humidity,and have a large operating range(33%-95%RH).They showed very good linearity in two regions and narrow hysteresis.Among them,Si-SBA-15 showed short response/recovery time.(4)Two kinds of porous silicons with different morphology have been prepared by magnesiothermal reduction,they consist of crystal silicon,and to a large extent maintained a morphology similar to that of the original template,and owned a regular pore structure.Tow kinds of porous silicons have sensitive characteristic for humidity,among them,the Si-SBA-15 sensor's sensitive characteristic is better.