XPS analysis and electrical conduction mechanisms of atomic layer deposition grown Ta2O5 thin films onto p-Si substrates

Abstract

Metal oxide semiconductor capacitors that incorporate tantalum pentoxide (Ta2O5) thin films as dielectric were fabricated via the atomic layer deposition (ALD) technique and characterized through TEM, XPS, C–V, and I–V measurements. TEM analysis revealed the amorphous phase of Ta2O5 films and the existence of an ultrathin SiOx layer in the Ta2O5/p-Si interface, also evidenced by XPS spectra. XPS analysis verified the stoichiometry of the ALD-deposited Ta2O5 films. Furthermore, XPS results indicate values of 2.5 and 0.7 eV for the conduction and valence band offsets of the Ta2O5/p-Si interface, respectively. I–V measurements, for positive and negative applied bias voltages, reveal that the conduction is governed by Ohmic, trap controlled space charge limited, and Schottky mechanisms depending on the applied voltage and temperature region. Through the analysis of Schottky emission data, the conduction band offset of Ta2O5/p-Si (φΒ) is calculated to be 0.6 eV, while the valence band offset is 2.6 eV, in very good agreement with the XPS results. The energy band diagram of Ta2O5/p-Si is constructed.

Oxidation of tantalum disulfide (TaS2) films for gate dielectric and process design of two-dimensional field-effect device

“…The oxidation rate was estimated to be 2.5 nm min −1 in this study. For ALD in recent studies, the deposition rates of Ta-oxide film were in the range of 0.95-7.5 nm cycle −1 , including the precursor insertion and purge time [25,26]. These synthesis rates are comparable to those in our study, demonstrating that our approach requires a sufficiently process time.…”

Improved Resistive and Synaptic Characteristics in Neuromorphic Systems Achieved Using the Double-Forming Process

“…In Figure 2a, the spin-orbit splitting of Zr 3d is equal to 2.4 eV, and the peak differences in binding energy confirm this [31]. Similarly, in Figure 2b, the response has been fitted to detectable compounds, while the spin-orbit splitting of Ta 4f is 1.8 eV [32]. The binding energy peak at 24.39 eV corresponds to TaON, thus verifying the presence of the TaON interfacial layer in the XPS analysis [33].…”

Interface band offset determination of ultra-thin oxides grown on TiO2 and ZnO by x-ray photoelectron spectroscopy

“…Two ultra-thin ZnO films of 0.6 and 1.0 nm were also prepared using four and six cycles respectively. The thickness of similar, up to 10 nm, films has been investigated by our team previously [29][30][31] and it was shown that the nominal growth rates are in agreement with the calculated ones. Also, films with thickness of at least 20 nm of Al 2 O 3 , ZrO 2 , HfO 2 and Ta 2 O 5 were prepared and will be noted as reference samples.…”

“…Although the Kraut method is usually applied for conductive samples, it has also been used for wide bandgap oxides [6,[46][47][48][49]. A comparison of the Kraut method with the results obtained from electrical measurements for the determination of the band offsets of the Ta 2 O 5 /Si interface, was recently published by our group, showing that the two methods compare well to each other [29]. The Kraut method can be summarized in equations ( 1)-( 3), where 'f', 's', 'ref' and 'int' refer to 'film', 'substrate', 'reference' and 'interface', respectively:…”