P-041

Eimutis Juzeliūnas

eimutis.juzeliunas@ftmc.lt

A. Šilėnas, L. Staišiūnas, P. Kalinauskas, K. Leinartas, A. Grigucevičienė, A. Lučun, S. Tutlienė

Center for Physical Sciences and Technology, (FTMC) Vilnius, Lithuania

Investigation of Interfacial Charging and Charge Transfer in Thin HfO2 Layers on Silicon Using Resistometry and Photoelectrochemistry

Oxide layers on silicon can help reduce surface recombination by providing chemical and electrical passivation, improving the efficiency of photovoltaic (PV) devices. In this study, we present a simple experimental method to analyze interfacial charge behavior at the Si/oxide interface.

Interfacial charging in crystalline p-Si with thin hafnia (HfO2) layers deposited using atomic layer deposition (ALD) and sol–gel techniques was investigated using transverse electric resistometry to detect charge accumulation in ambient conditions. The current–voltage (I–V) characteristics of the samples resembled those of a p-n junction, conducting when forward-biased and non-conducting when reverse-biased. The data suggest that the silicon surface at the Si/HfO2 interface was negatively charged.

In an electrolyte environment interfacial charging was studied by probing the interface with photoinduced electrons and measuring the photoresponses of capacitance, potential, resistance, and current density. The photocapacitance vs. electrode potential measurements identified the photopotential at which the excess charge in the Si space charge region was minimal. Capacitance inversion during negative polarization indicated a shift in surface charge from positive to negative.

At open circuit, a positive photopotential jump was observed under illumination, followed by a slow relaxation back to the initial value in darkness. When illumination was turned off, the potential dropped and returned to its initial state in the dark. This behavior suggests that photoelectrons penetrate the oxide layer, balancing the electrode photopotential. The backward potential shift in the dark reflects the negative charge accumulated in the oxide during illumination.

The cathodic photocurrent was strongly suppressed by the HfO2 layer during the hydrogen evolution reaction (HER). It was determined that charge transfer inhibition was primarily due to interfacial charging effects rather than the electrical resistance of the oxide layer.

The proposed methodology can be applied to a wider range of passivating oxides on silicon, such as Nb2O5, TiO2, and Al2O3.