Table 1.
Overview of the structure and electrical properties of TiO2-based memristors obtained by various synthesis methods.
| Synthesis method | Deposition method (annealing temperature, time, and atmosphere) | Structure | Feature size*, μm2 (TiO2 phase) | Thickness, nm (particle size, nm) | , V | ROFF/RON | Application | Retention time, s (switching time, s) | Reference |
|---|---|---|---|---|---|---|---|---|---|
| Sol–gel | Spin coating (550°C, 10 h, air) | Cellular, Al/TiO2/FTO | 2 × 106 (anatase) | 35 | 3.9 | 2 × 105 | General | 104 (N/D) | (Tao et al., 2020) |
| Sol–gel | Inkjet (200°C, 2 h, Air) | Planar, Au/TiO2/Au | 3 (anatase) | 400 (7***) | ~4 | ~20 | Cell biology | N/D | (Illarionov et al., 2019) |
| Sol–gel | Drop casting (N/D) | Crossbar, Ag/TiO2/Cu | 4 × 106 (amorphous) | 4.5 × 104 | 0.5 | 107 | γ-ray sensor | 4 × 104 (50 ÷ 360) | (Abunahla et al., 2018) |
| Sol–gel | Inkjet (150°C, 15 min, N2) | Cellular, Ag/TiO2/Ag/PET | 3,600 | 10–160 | ~1.5 | 500 | Mechanical sensor | N/D | (Vilmi et al., 2016) |
| Sol–gel | Spin coating (500°C, 1 h, air) | Cells array, Al/TiO2/FTO | 2 × 105 (anatase) | 100 | ~1.8 | >300 | RRAM | 104 (10) | (Hu et al., 2020) |
| Hydrothermal | Dip coating (450°C, 2 h, air) | Sandwiched, Ag/TiO2/Al | N/D (anatase) | 265 | 0.7 | 100 | RRAM | N/D | (Dongale et al., 2014) |
| Hydrothermal | Dip coating (500°C, 3 h, air) | Sandwiched, Al/TiO2/Ti | 7.9 × 105 (anatase nanowires) | N/D | ~3 | 70 | RRAM | 104 (N/D) | (Xiao et al., 2017) |
| Hydrothermal | Dip coating (300°C, 2 h, air) | Sandwiched, Ag/TiO2/FTO | 1.3 × 107 (rutile + anatase, rutile) | 7,000 | 1.2 | >10 | RRAM | 4 × 106 (N/D) | (Irshad et al., 2019) |
| Solid state, 2D colloid | Dip coating | Crossbar, Al/TiO2/Pt/Ti/SiO2/Si | 4 | 2 | 0.5 ÷ 1.5 | 106 | RRAM | 104 (20 × 10−9) | (Dai et al., 2017) |
| Thermal oxidation | – | Sandwiched, Ir/TiO2/TiN | N/D | 4 | >1.5 (set) | ~100 | RRAM | 104 (10−7) | (Park et al., 2011) |
| Thermal oxidation | – (650°C, 1 h, air) |
Cellular, Ti/TiO2/Ti | ~3 × 106 (rutile) | 400 (50)**** | 2 | ~4 | Humidity sensor | 6 × 105 (~10−2) | (Hossein-Babaei and Alaei-Sheini, 2016) |
| Anodizing | – | Cellular, Cu/TiO2/Ti | 4 | 8, 11, 29 | −1.5 | <80 | RRAM | N/D | (Aglieri et al., 2018) |
| Anodizing | – (550°C, 1 h, N2/H2 24/1) |
Cells array, Pt/TiO2/Ti | ~108 | <100 | <1 | ~56 | General | N/D | (Miller et al., 2010) |
| PVD, ALD | – | Crossbar, Pt/TiO2/HfO2/Pt | 4 × 10−6 | 7 | ~1.8 | 450 | RRAM, computing | 120 (N/D) | (Pi et al., 2019) |
| PEALD | – | Crossbar, Al/TiO2/Al | 3,600 (amorphous) | 13 | 2.1 | >100 | RRAM | N/D | (Jeong et al., 2010b) |
| PEALD | – | Crossbar, Pt/Ni/TiO2/Al2O3/Pt | 4,900 (amorphous) | 12 | ~0.5 ÷ 1.5 | ~100 | RRAM | N/D | (Jeong et al., 2010a) |
| PVD/RMS | – (600, 800°C, 3 h, air) |
Crossbar, Pt/TiO2/Pt | N/D (anatase) | 2,000 (40–50)*** | ~0.2 ÷ 1.0 | <6 × 105 | H2 sensor | N/D (5) | (Haidry et al., 2017) |
| PVD/RFS | – (400°C, 15 min, N2) |
Crossbar, Ni/TiO2/Ni | 1.1 (anatase) | 10 | ~0.8 | 104 | RRAM | N/D | (Cortese et al., 2016) |
| PVD/RS | – | Cellular, Al/TiO2/Au | 100 | 50 | 0.5 | 12 | General | N/D (10−3) | (Ghenzi and Levy, 2018) |
| PVD/RS | – | Crossbar, Pt/TiO2/Pt/Cr | 2.25, 9 (amorphous and anatase) | 30 (10)*** | ~0.5 | ~100 | RRAM | N/D | (Strachan et al., 2013) |
| PMCS | – | Planar, glass/TiO2/Al | 1.77 × 108 (rutile and anatase) | 30 | N/D | N/D | Bio-interface | N/D | (Roncador et al., 2017) |
| PLD | – | Cellular, Cu/TiO2/Pt | 1.26 × 105 | 100 | ~0.2 | ~3 × 103 | RRAM | 100 (250 × 10−9) | (Sahu et al., 2020) |
~, estimated or recalculated values;
*
electrode area;
**
threshold voltage;
***
by Scherrer equation;
****
by SEM, scanning electron microscopy.
2D, two-dimensional; ALD, atomic layer deposition; MRS, magnetron reactive sputtering; PEALD, plasma-enhanced atomic layer deposition; PVD, physical vapor deposition; RFS, radio frequency sputtering; ROFF/RON, resistive switching ratio; RRAM, resistive random-access memory; RS, reactive sputtering; VT, threshold electroforming voltage.