Tunable Low Crystallinity Carbon Nanotubes/Silicon Schottky Junction Arrays and Their Potential Application for Gas Sensing

Abstract

Highly ordered nanostructure arrays have attracted wide attention due to their wide range of applicability, particularly in fabricating devices containing scalable and controllable junctions. In this work, highly ordered carbon nanotube (CNT) arrays grown directly on Si substrates were fabricated, and their electronic transport properties as a function of wall thickness were explored. The CNTs were synthesized by chemical vapor deposition inside porous alumina membranes, previously fabricated on n-type Si substrates. The morphology of the CNTs, controlled by the synthesis parameters, was characterized by electron microscopies and Raman spectroscopy, revealing that CNTs exhibit low crystallinity (LC). A study of conductance as a function of temperature indicated that the dominant electric transport mechanism is the 3D variable range hopping. The electrical transport explored by I–V curves was approached by an equivalent circuit based on a Schottky diode and resistances related to the morphology of the nanotubes. These junction arrays can be applied in several fields, particularly in this work we explored their performance in gas sensing mode and found a fast and reliable resistive response at room temperature in devices containing LC-CNTs with wall thickness between 0.4 nm and 1.1 nm.

The Synthesis of Sponge-like V2O5/CNT Hybrid Nanostructures Using Vertically Aligned CNTs as Templates

“…To explore this effect, Raman spectra were measured in the ranges where CNTs exhibit their characteristic resonances, on the sample coated with 50 nm V and oxidized at 400 °C (labeled as “VACNT_50V_400”), together with the other three samples: as-grown VACNTs (labeled as “VACNT”), VACNTs without vanadium oxidized in an O 2 atmosphere at 400 °C (labeled as “VACNT_400”), and another VACNT sample oxidized at 500 °C (labeled as “VACNT_500”). These spectra, shown in Figure 5 a, are characteristics of CNTs with low crystallinity, with the exception of the spectrum of the sample with the V coating, indicating the existence of CNTs with a higher graphitization level [ 47 , 48 , 49 ]. The following quantitative analysis, based on the fit of these spectra, supports this observation.…”

Application of Two-Dimensional Materials towards CMOS-Integrated Gas Sensors

“…At the interface, a dipole layer is formed, changing the surface potential of the gate and shifting the threshold voltage V t of the FET. This feature of the catalytic metal films is also used at the main sensing principle in Schottky-barrier gas sensors [ 140 , 141 , 142 ]. Furthermore, it should also be noted that these types of sensors are relatively easy to integrate with CMOS fabrication, albeit the inclusion of catalytic metals such as gold or platinum can be problematic.…”

High sensitivity carbon monoxide detector using iron tetraphenyl porphyrin functionalized reduced graphene oxide

“…Various researchers across the globe have been investigating numerous materials to achieve optimal sensing performance from gas sensors for the detection of CO [1][2][3][4][5][6]. For example, in recent years, carbon-based materials such as graphene and carbon nanotubes (CNTs) have stepped forward as superior materials in the gas sensing aspect due to their high surface-to-volume ratio and exceptional electrical properties [7][8][9][10][11][12][13][14]. Reduced graphene oxide has often been used for sensing applications because of its semiconducting nature instead of pristine graphene, which exhibits conducting characteristics [15][16][17][18][19].…”