Metal electrode dependent field effect transistors made of lanthanide ion-doped DNA crystals

We fabricated lanthanide ion (Ln³⁺, e.g. Dy³⁺, Er³⁺, Eu³⁺, and Gd³⁺)-doped self-assembled double-crossover (DX) DNA crystals grown on the surface of field effect transistors (FETs) containing either a Cr, Au, or Ni electrode. Here we demonstrate the metal electrode dependent FET characteristics as a function of various Ln³⁺. The drain-source current (I_ds), controlled by the drain-source voltage (V_ds) of Ln³⁺-doped DX DNA crystals with a Cr electrode on an FET, changed significantly under various gate voltages (V_g) due to the relative closeness of the work function of Cr to the energy band gap of Ln³⁺-DNA crystals compared to those of Au and Ni. For Ln³⁺-DNA crystals on an FET with either a Cr or Ni electrode at a fixed V_ds, I_ds decreased with increasing V_g ranging from -2 to 0 V and from 0 to +3 V in the positive and negative regions, respectively. By contrast, I_ds for Ln³⁺-DNA crystals on an FET with Au decreased with increasing V_g in only the positive region due to the greater electronegativity of Au. Furthermore, Ln³⁺-DNA crystals on an FET exhibited behaviour sensitive to V_g due to the appreciable charge carriers generated from Ln³⁺. Finally, we address the resistivity and the mobility of Ln³⁺-DNA crystals on an FET with different metal electrodes obtained from I_ds-V_ds and I_ds-V_g curves. The resistivities of Ln³⁺-DNA crystals on FETs with Cr and Au electrodes were smaller than those of pristine DNA crystals on an FET, and the mobility of Ln³⁺-DNA crystals on an FET with Cr was relatively higher than that associated with other electrodes.