Infrared Signatures for Phase Identification in Hafnium Oxide Thin Films

Structure and stability of La- and hole-doped hafnia with/without epitaxial strain

“…More precisely, we used the HSE06 method to calculate the PDOS of the pure m and o phases (see figure S1). The band gaps of pure m and o phases are 5.54 and 5.98 eV, which is consistent with previous work [68,71,72]. While the PBEsol functional results underestimate the band gaps, the relative distribution of the PDOS is comparable to that obtained by the HSE06 method, which suggests its suitability for qualitative analysis [73].…”

“…Simultaneously, the energy of the ao phase is slightly lower than that of the o phase. However, considering that both the o and ao phase could be observed experimentally [68,69], and they can undergo mutual transformation through oxygen displacement, we will primarily focus on discussing the m and o phase.…”

Bipolar Plasticity in Synaptic Transistors: Utilizing HfSe2 Channel with Direct-Contact HfO2 Gate Dielectrics

“…Notably, this current persists in its incremental/decremental trend under the accumulation of negative (positive) bias voltage, reinforcing the assertion that longer intervals of pulse do not abate the synaptic response's progressive trajectory. This observation alludes to an intrinsic polar electric field's sustained influence, validated through P-V measurements that substantiate the ferroelectric nature of the examined HfO 2 films (as shown in Figure 4b) [26]. Figure 4b illustrates the ferroelectric characteristics of HfO 2 thin films at various thicknesses (14 nm, 20 nm, and 30 nm), as shown by their polarization-voltage (P-V) loops.…”

Internal Photoemission Spectroscopy Measurements of Interfacial Energy Barriers in Operating TaN/Hf0.5Zr0.5O2/TaN Metal/Ferroelectric/Metal (MFM) Devices

“…It corresponds to the band gap of annealed ALD HZO measured via spectroscopic ellipsometry (5.2 eV), and is less than band gap values reported for either ALD HfO 2 or ZrO 2 (5.6 and 5.4 eV, respectively) measured via reflection electron energy loss spectroscopy (REELS). , The onset of photoconduction occurred at approximately 5.2 eV regardless of electric field sweep direction for both bottom and top electrodes in pristine, woken, and both negative and positive poled devices, indicating that the transformations in the crystal structure due to the waking and poling operations did not appreciably change the bandgap. The onset of photoconduction occurred at higher energy than the 4.9 eV reported by Jenkins et al for IPE of unannealed HZO deposited by thermal ALD, which may have been impacted by band tailing, V O + density, or relatively higher monoclinic phase fractions which have a lower bandgap than the orthorhombic phase. , …”

“…The waking process resulted in an increase in φ bn of the top interface, from 2.6 to 2.9 eV, but no significant change in the bottom barrier. The waking procedure opens the ferroelectric hysteresis loop and involves conversion of the material from tetragonal and/or antipolar orthorhombic to polar orthorhombic (ferroelectric) and is thought to involve the redistribution/movement of oxygen vacancies (which tend to be positively charged). ,,, As the two orthorhombic hafnia crystal phases have similar bandgaps and the tetragonal phase has a much larger bandgap, , the increase in the top electrode electron φ bn is likely due to a redistribution of V O + away from the top interface and toward the bulk of the material. The device thus appeared more symmetric with φ bn of 2.8 and 2.9 eV for the top and bottom electrodes, respectively.…”