Field emission Properties of Tungsten Oxide NanowiresSaqib, Muhammad (Avtor) Remškar, Maja (Mentor) Tunsten oxidesNanowiresRaman spectroscopyKelvin probe force microscopyWork functionField emissionField enhancement factorWe studied field emission of electrons from two types of single crystalline tungsten oxide, W5O14 and W18O49 nanowires, which were synthesized by iodine transport method. The morphology, structure and work functions of these nanowires were investigated and compared. Raman spectrum of the W5O14 nanowires was measured for the first time. The work function of the W5O14 (4.29-4.34 eV) and W18O49 (4.55-5.57 eV) nanowires have been measured by Kelvin probe force microscopy in non-contact atomic force microscopy in ultra-high vacuum and with nanometre spatial resolution. The new methods were figured out in order to mount/fix the nanowires on different tip holders for field emission testing. Field emission measurements were carried out using individual W5O14 and W18O49 nanowires of 140-160 nm and 0.2-3 μm in diameter, respectively. The experiment were performed in two different, near field and far field regimes, in ultra-high vacuum chambers at a level of 1-3×10-9 mbar in different measurements setups. The obtained FE curves were analysed in the framework of the Fowler-Nordheim theory. Considering an average work function of 4.3 eV for W5O14, the field enhancement factors of about 110 ± 10, 180 ± 25 and 210 ± 30 were calculated at 2, 4 and 5 μm distances, respectively in the near-field regime. At macroscopic distances (⡥1 mm), the Fowler-Nordheim theory revealed unrealistically high field enhancement factors: for W5O14 at 1 mm it was 17000 ± 500, and for W18O49, the field enhancement factors were 5050 ± 30 and 6450 ± 30 at 600 μm and 800 μm emitter-collector distance, respectively. Therefore, another model proposed by R. Smith was discussed. Since the work function of a single nanoemitter has been measured, the field enhancement factors were obtained based on a realistic work function values. This is a key step towards quantifying the field emission properties of W5O14 nanowires with well-defined structure. The rigidness, low work function and high field enhancement factor of the W5O14 nanowires allow them to be considered as an effective candidate for electron sources in different applications, especially in field emission devices.20202020-08-21 19:09:04Doktorsko delo/naloga118128sl