A Variable Response Phosphine Sensing Matrix Based on Nanostructure Treated p and n-Type Porous Silicon Interfaces

Abstract

We study the dynamic interplay as PH 3 interacts at room temperature to contribute electrons to nanostructure modified p and n-type porous silicon (PS) interfaces. A nanopore coated microporous interface is treated to form TiO 2 , SnO x , Cu x O, and Au x O (x 1) nanostructured centers deposited in fractional coverage on the PS interface. Relative sensitivities of the surface sites are measured under 2-5 and 10 ppm PH 3 exposure. The interaction with two p-type nanostructure decorated boron-doped interfaces demonstrates enhancement of sensitivity relative to undecorated PS. The results are explained using the inverse hard/soft acid/base (IHSAB) principle, combining the tenants of acid/base chemistry and semiconductor physics. Analyte coupling to the majority charge carriers of the extrinsic semiconductor determines the nature of directed electron transduction as it induces a change in conductance. As applied, the nanostructured metal oxides serve as gateways, forcing a dominant electron transduction (versus chemisorption) at the decorated extrinsic semiconductor interface. A study of gold clustered oxide depositions on p-type (1-3 -cm) PSdemonstrates that an optimal fractional deposition can be attained and should not be exceeded to avoid crosstalk between the deposited nanoparticles. It appears that phosphine can be converted on interaction with phosphorous doped n-type PS. A reversal of the response signal observed with increased PH 3 concentration, considered within the IHSAB model, suggests that the conductance might be associated with the formation of the electron withdrawing PH 2 radical.

Detection of Liquid Organic Solvents on Metal Oxide Nanostructure Decorated Porous Silicon Interfaces

“…In Figure S10, we demonstrate that the metal oxide nanostructures greatly affect the complex impedance. However, it should be noted that this effect is size dependent limited to nanoscale particles. , Therefore, the size and level of deposition of the metal oxide nanostructures must be at a level low enough to produce electronically independent particles . Husairi et al have investigated the influence of a layer of ZnO nanostructures on the interactions of a PSi interface with liquid ethanol.…”

“…7,11 Therefore, the size and level of deposition of the metal oxide nanostructures must be at a level low enough to produce electronically independent particles. 24 Husairi et al 13 have investigated the influence of a layer of ZnO nanostructures on the interactions of a PSi interface with liquid ethanol. Through an analysis of the complex impedance curves and complementary equivalent circuit elements, Husairi et al 13 demonstrated that the ZnO nanostructures increased both the real and imaginary parts of the complex impedance.…”

Nanostructure Directed Detection of Acidic SO2and Its Transformation to Basic Character: Suggested Transient Formation of SO3−, Impedance by Xylene

“…This required interaction is varied for a given system by studyng the conductometric sensor response as a function of metal oxide deposition concentration. 9 Typical nanostructured metal oxide deposited island sites range between 10 and 20 nm as, within the constraints, the size range influences the observed interactions. 8,10 the highly accurate repeat placement of the depositions is not required.…”

“…2,4 "Deposited" nanostructured island sites serve the role of guiding gateways to force a dominant electron transduction (vs. chemisorption) at the decorated extrinsic semiconductor interface. The selection of these nanostructures and the reversible interaction they introduce for sensor applications is predicted by the IHSAB model, 2,[4][5][6][9][10][11][12][13][14] which complements the tenants of the HSAB concept, 15 and couples analyte/interface acid-base interactions with the properties of the majority charge carriers in an extrinsic semiconductor. Based on the reversible interaction of hard acids and bases with soft bases and acids, the IHSAB principle enables the selection of interacting materials that do not form strong covalent or ionic chemical bonds, thus it represents the inverse of the HSAB model 15 for significant bond formation based on strong ionic (hard acid/base) or covalent (soft acid/base) interactions and chemical bond formation.…”

Development of a Fermi Energy Distribution Based Adsorption Isotherm for Response Simulation of Nanostructure Decorated Porous Silicon Substrates

“…In order to remove the noise, a moving average is used. 31,32 The moving average works by taking the average of a fixed number of previous points in the data set and using this averaging to smooth the data. The moving average reduces the high frequency noise in the system, smoothing out the derivatives.…”