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Povzetek: Molybdenum disulfide (MoS2) has emerged as a promising material for next-generation electronics and optoelectronic devices. MoS2 nanotubes (NTs) and their collapsed ribbon-like shapes (collapsed NTs) synthesized via chemical vapour transport (CVT) under chemical equilibrium typically exhibit low structural defect densities. However, defects and surface damage can arise during device fabrication or operation, leading to a significant degradation in performance, stability, and operational lifetime. These imperfections also induce hysteresis, which adversely affects the device switching behaviour. While the influence of charge trapping at the MoS2/substrate interfaces, on the MoS2 surface, and at intrinsic defects, such as sulfur vacancies and dangling bonds, on device performance has been extensively studied, MoS2 NTs, with their unique curved morphology, introduce additional charge-trapping mechanisms not observed in planar MoS2 structures. In this work, a combination of scanning tunnelling microscopy (STM), Kelvin probe force microscopy (KPFM), and conductive atomic force microscopy (cAFM) was employed to examine how structural irregularities, including terminated layers, surface-grown flakes or NTs, and highly strained areas, affect charge injection, redistribution, and the resulting effects on electrical characteristics in collapsed NTs. The results reveal that structural defects act as charge traps, scattering centres, and transport barriers, giving rise to a reduced carrier mobility, localized charge accumulation, and spatially inhomogeneous charge distribution. These findings underscore the crucial role of structural and electrical characterization with nanoscale resolution in the design of defecttolerant, high-performance devices based on transition metal dichalcogenides (TMDs)
Ključne besede: nanoscale characterization, structural defects, charge trapping, nanotubes
Objavljeno v DiRROS: 26.11.2025; Ogledov: 535; Prenosov: 73
Celotno besedilo (1,00 MB)

Povzetek: Molybdenum disulfide (MoS2) is a promising material for future high-performance and ultra-low-power electronics. Growth from a vapor phase at chemical equilibrium enables the production of crystals possessing a relatively low density of structural defects. Besides thin MoS2 flakes, MoS2 nanotubes (NTs) and collapsed NTs in the shape of nanoribbons (NRs) are also synthesized in the same growth process. Here, we present the first study on the structural and electrical properties of the NRs. High resolution electron microscopy revealed a chiral structure of the NRs with no peculiarities at the inner interface where both walls are in contact. In contrast, resonant Raman spectroscopy revealed the presence of bands typical of a few layers thick MoS2, suggesting that some of the layers of the NR are partially split. Contact current imaging spectroscopy (CCIS) revealed longitudinal wrinkles on the NR surface, with elevated regions found to be more conductive than the depressed areas. The edges of the NR, where molecular layers are strongly curved but not broken, exhibit varying conductivity. While some parts exhibit zero conductivity, others show much higher conductivity than the central part of the NR, suggesting an electron confinement effect. Charge injections strongly altered the NR’s work function and induced changes in the NR’s topography. The surface wrinkling was intensified, and the NR tended to rotate around its longitudinal axis. This rotation is explained as the reverse piezoelectric effect.
Objavljeno v DiRROS: 16.05.2025; Ogledov: 647; Prenosov: 335
Celotno besedilo (2,34 MB)
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