Ionic liquid gating can markedly modulate the materials carrier density so as to induce metallization, superconductivity, and quantum phase transitions. One of the main issues is whether the mechanism of ionic liquid gating is an electrostatic field effect or an electrochemical effect, especially for oxide materials. Recent observation of the suppression of the ionic liquid gate-induced metallization in the presence of oxygen for oxide materials suggests the electrochemical effect. However, in more general scenarios, the role of oxygen in ionic liquid gating effect is still unclear. Here, we perform the ionic liquid gating experiments on a non-oxide material: two-dimensional ferromagnetic Cr2Ge2Te6. Our results demonstrate that despite the large increase of the gate leakage current in the presence of oxygen, the oxygen does not affect the ionic liquid gating effect (< 5 % difference), which suggests the electrostatic field effect as the mechanism on non-oxide materials. Moreover, our results show that the ionic liquid gating is more effective on the modulation of the channel resistances compared to the back gating across the 300 nm thick SiO2.
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