Work Function Measurements of Carbon Structures Using Ultraviolet Photoelectron Spectroscopy

The work function of carbon-based materials is crucial in understanding the electronic properties, offering critical insights for optimizing device performance and advancing electronic applications. The work function of diamond-like carbon (DLC), Q-carbon, and diamond is measured using ultraviolet photoelectron spectroscopy (UPS). Three DLC films having different sp²/sp³ content (I_D/I_G ratios 0.43, 0.87, and 1.61) are grown using pulsed laser deposition, and the Q-carbon films are fabricated using subsequent pulsed laser annealing of the DLC films. Moreover, the diamond films are deposited using hot filament chemical vapor deposition (HFCVD). The compositional analysis of the films is performed using Raman spectroscopy, and the formation of Q-carbon is confirmed through Raman spectroscopy and scanning electron microscopic (SEM) analysis. The bandgap measurement using the Tauc plot demonstrates the bandgap of the DLC films to range from 2.56 eV to 3.77 eV, while the bandgap of Q-carbon is measured to be 3.7 eV. The work function measurement reveals the values to range from 3.91 eV to 4.18 eV for the DLC films. Additionally, the work function of Q-carbon is calculated to be 3.82 eV from experimental measurements, while the DFT simulations provide a value of 3.62 eV. Finally, the diamond film's work function is measured at 4.54 eV. Overall, the results reveal insights into the relationship between structural characteristics and work function, providing valuable information for optimizing the performance of these materials in electronic and optoelectronic technologies.