Nanoengineered chemiresistors: the interplay between electron transport and chemisorption properties of morphologically encoded SnO₂nanowires

Abstract

The transport properties and gas-sensing performance of chemiresistors based on quasi-1D, single-crystal, SnO2 nanostructures with deliberately synthesized (encoded) segmented morphology are explored. Such nanostructures were obtained using programmable modulation of the gas supersaturation ratio during their growth. Using hydrogen and oxygen as model reducing and oxidizing gases, we show that the responsiveness of these structurally modulated nanowires to gases is improved over that of straight nanowires of the same average diameter. This is due to the presence of small-diameter segments, which dominate the nanostructure’s transport properties and to the better tolerance of such nanostructures towards contact effects. The narrow segments approximate the excellent responsiveness of ‘necks’ between particles in traditional thin film gas sensors but with the significant advantage of greater morphological integrity and stability.

Insight into the Role of Oxygen Diffusion in the Sensing Mechanisms of SnO2 Nanowires

“…2) [27] and a depletion layer of width l ¼ 10 nm was estimated, which is in good agreement with literature data. [7,28] If thin nanowires (r ! l) are studied, we approach to the deep depletion condition (also called in the literature flat band situation [4] ), in which surface phenomena entirely modify the bulk properties (i.e., the number of free electrons N d ) and thus Equation 3 can be rewritten as, [4,29] Sð%Þ ¼…”

“…[1][2][3][4][5][6] In particular, chemical sensing is favored by their high surface-tovolume ratio. [4] In the last years, many groups have devoted their efforts to determine the ultimate sensing capabilities of these nanomaterials [1][2][3][4][5][6][7][8][9] and to obtain theoretical models able to describe their experimental responses. [3,4,6] On the other hand, present nanofabrication techniques enable the development of new prototypes which combine metal oxide nanowires with well-established microelectronic technologies.…”

Contactless monitoring of the diameter-dependent conductivity of GaAs nanowires

“…The conductivity of NWs, one of the most important properties exploited in numerous applications, becomes extremely sensitive to the status of the surface with decreasing NW width, and dramatic conductivity changes can be observed when the Debye length becomes comparable to the NW radius [4]. Along with presence of adsorbates and charged surface states [5,6], other factors that may affect the conductivity include the (i) reduced mobility due to enhanced phonon or surface scattering [7,8], (ii) edge effects due to unsaturated bonds of the surface atoms [9], (iii) size-imposed limits to the effective doping concentration [9,10], (iv) size-dependence of depletion width [11], band-gaps [12,13], and recombination barriers [14].…”

Fabrication of SnO2 one-dimensional nanosturctures with graded diameters by chemical vapor deposition method

“…Owing to surface effect and size-confinement effect, SnO 2 one-dimensional (1D) nanostructures (such as nanowires, nanobelts and nanorods) have been shown to exhibit much more abundant physical and chemical properties than their bulk crystal, and then have even wider potential applications. Therefore, SnO 2 1D nanostructures have attracted considerable attention and provoked extensive researches [5][6][7][8][9]. SnO 2 1D nanostructures have been synthesized successfully by various methods, such as chemical vapor deposition (CVD) [10,11], hydrothermal method [12], microemulsion technology [13], laser ablation [14], etc.…”