Fabrication and Evaluation of Organic Field-Effect Transistors (OFETs) : Fullerene C70

Fabrication and evaluation of vacuum-deposited Fullerene C70 [F1233]-based OFETs

< Substrate>

• HMDS-treated Si/SiO₂ (thickness of SiO₂: 200 nm)
• OTS-treated Si/SiO₂ (thickness of SiO₂: 200 nm)

< Self-Assembly Monolayer (SAM) Treatment>

• 1,1,1,3,3,3-Hexamethyldisilazane (HMDS) [H0089]
  
  1. Piranha etching (H₂SO₄:H₂O₂=4:1, 80ºC, 2h)
  2. Ultrasonication (Deionized water, Acetone, IPA, 10 min each)
  3. Exposure to vapor (IPA, 3 min)
  4. UV/O₃ treatment (1 h)
  5. Immersion in HMDS (16 h, N₂)
  6. Ultrasonication (Toluene, Acetone, IPA, 10 min each)
• n-Octyltrichlorosilane (OTS) [O0168]
  
  1. Piranha etching (H₂SO₄:H₂O₂=4:1, 80ºC, 2h)
  2. Ultrasonication (Deionized water, Acetone, IPA, 10 min each)
  3. Exposure to vapor (IPA, 3 min)
  4. UV/O₃ treatment (1 h)
  5. Immersion in OTS solution (0.01 M toluene, 16 h, N₂)
  6. Ultrasonication (Toluene, Acetone, IPA, 10 min each)

< Vacuum Deposition>

• Deposition rate of C70 [F1233] 0.2 Å/s (under a pressure of∼10⁻⁵ Pa)
• Substrate temperature during deposition: RT
• Deposition rate of Au: 0.2 Å/s (under a pressure of∼10⁻⁵ Pa)

< Device configuration>

• [n⁺-Si/SiO₂ (200 nm) / C70 [F1233] (40 nm) / Au (40 nm)]
• Top-Contact Bottom-Gate Type (TCBG)
• Channel Length: 50 μm
• Channel width: 1.5 mm

< Evaluation condition>

• Under N₂
• Field-effect mobilities (μ) were determined from the transfer curves in the saturation regime using the following equation:I_D = (W/2L) μ Ci (V_G − V_th)²