Structure, Surface Morphology, Chemical Composition, and Sensing Properties of SnO2 Thin Films in an Oxidizing Atmosphere

Abstract

We conducted experiments on SnO2 thin layers to determine the dependencies between the stoichiometry, electrochemical properties, and structure. This study focused on features such as the film structure, working temperature, layer chemistry, and atmosphere composition, which play a crucial role in the oxygen sensor operation. We tested two kinds of resistive SnO2 layers, which had different grain dimensions, thicknesses, and morphologies. Gas-sensing layers fabricated by two methods, a rheotaxial growth and thermal oxidation (RGTO) process and DC reactive magnetron sputtering, were examined in this work. The crystalline structure of SnO2 films synthesized by both methods was characterized using XRD, and the crystallite size was determined from XRD and AFM measurements. Chemical characterization was carried out using X-ray photoelectron (XPS) and Auger electron (AES) spectroscopy for the surface and the near-surface film region (in-depth profiles). We investigated the layer resistance for different oxygen concentrations within a range of 1–4%, in a nitrogen atmosphere. Additionally, resistance measurements within a temperature range of 423–623 K were analyzed. We assumed a flat grain geometry in theoretical modeling for comparing the results of measurements with the calculated results.

Adsorption of the non-steroidal anti-inflammatory drug (ibuprofen) onto biochar and magnetic biochar prepared from chrysanthemum waste of the beverage industry

“…The signal at 200.4 eV was attributed to Cl–C bonds, 51 while the 198.9 eV peak is assigned to alkali chloride. 52 For the Fe 2p of magnetic biochar, the peak at 711.3 eV represents Fe 3+ in Fe 3 O 4 . 49 Cao et al reported that a peak at 718.4 eV was ascribed to a Fe 2p 3/2 satellite peak and peak at 724.4 eV attributed to Fe 2p 1/2 of γ-Fe 2 O 3 .…”

Highly Sensitive and Selective Hydrogen Gas Sensor with Humidity Tolerance Using Pd-Capped SnO2 Thin Films of Various Thicknesses

“…Sensor L2 exhibited a higher response than L1 and L3 sensors, which may be attributed to the non-stoichiometric composition of tin and oxide as deduced from EDAX Figure 3 and XPS spectra Figure 4 [15]. When the sensor comes in contact with the gas under detection, the gas molecules react with the adsorbed oxygen anions.…”

“…The RMS values of L1, L2, and L3 sensors are also listed in Table 1. The ratio of atomic% of [O]/[Sn] = 1.3 indicated a non-stoichiometric composition in sensor L2 [15], and the atomic % of Pd 3d, Sn3d, and O1s were obtained as 7.76%, 10.89% and 14.2%, respectively.…”

“…Yulin Kong et al shows how SnO 2 nanostructure affect the gas-sensing properties of adsorbed oxygen [14]. W. Izydorczyk et al stated that sensor selectivity and sensitivity can be modified by adding noble elements to the sensor material in small quantities [15]. Furthermore, it is also noted that the performance of gas sensors based on two or more components is typically much better than single-component sensors which is reported by Zhang et al [16].…”

“…This XPS analysis revealed that the majority of Pd atoms are present as PdO and Pd metal species at the surface and form a heterostructure with SnO 2 thin films[36,37].The XPS high-resolution spectra of the O 1s region (Figure4d) consist of an asymmetrical peak, which was deconvoluted into two peaks indexed to O 1s[38]. One of them, centered at 529.84 eV, corresponds to oxygen, while the other peak, having a higher binding energy (531.85 eV), is ascribed to the adsorbed oxygen bonded to the material's surface, which plays a vital role in the sensing mechanism[38].The ratio of atomic% of [O]/[Sn] = 1.3 indicated a non-stoichiometric composition in sensor L2[15], and the atomic % of Pd 3d, Sn 3d, and O 1s were obtained as 7.76%, 10.89%, and 14.2%, respectively.…”