Table 2 Surface oxides observed on fabricated transmon qubits
From: Systematic improvements in transmon qubit coherence enabled by niobium surface encapsulation
Substrate | Film | Surface Encapsulation | Surface Oxide | Thickness | Average T1 (μs) |
|---|---|---|---|---|---|
Sapphire | Nb | - | Nb2O5 | 3–5 nm | 40 |
Sapphire | Nb | Ta | Ta2O5 | 3–5 nm | 120 |
Sapphire | Nb | Al | AlOx | 2–4 nm | 75 |
Sapphire | Nb | TiN | TiOx | 1–2 nm | 72 |
Sapphire | Nb | Au | Not Observed | - | 114 |
Silicon | Nb | - | Nb2O5 | 1–2 nm | 110 |
Silicon | Nb | Ta | Ta2O5 | 5–7 nm | 200 |
