Uvisel

The thickness of the film deposited on the Si substrate was measured using spectroscopic ellipsometry (UVISEL, Horiba, Kyoto, Japan). XPS (Theta Probe, Thermo Fisher Scientific Co., Waltham, MA, USA) was used to analyze the chemical bonding of the HfO_x films and to ascertain the presence or absence of La in the HfO_x films. The morphological properties of the deposited films were characterized by AFM (XE-100, Park Systems, Suwon, Korea). Furthermore, the crystalline phase and crystallite size and orientation were determined by GI-XRD (SmartLab, Rigaku, Tokyo, Japan) and TEM (Tecnai F20 G², FEI, Hillsboro, OR, USA). For the cross-sectional TEM image, a sample was prepared using the focused ion beam system, and for the plan view TEM image, samples were prepared using the ion milling system.

The thickness of the films was measured by using ellipsometry (Horiba Uvisel). For electrochemical characterization, the SiC and Si electrodes were assembled into CR2016-type coin cells with Celgard 2400 as separator, 1 M LiPF₆ dissolved in ethylene carbonate/dimethyl carbonate (v/v = 1 : 1) as electrolyte, and Li foil as counter electrode. Cyclic voltammetry was recorded at a scanning rate of 0.1 mV s⁻¹ between 0 V and 3 V versus Li/Li⁺ (CHI 660E). Galvano-static cycling was carried out between 0.01 V and 3.0 V versus Li⁺/Li (Land CT2001A). To examine the film properties after electrochemical cycling, the anode electrodes were took out from the coin cells after 100 charge/discharge cycles and dried in an Ar ambient. The crystalline structures of the films were investigated by X-ray diffraction (XRD, Bruker D8 Advance). The morphologies of the films were characterized by scanning electron microscopy (SEM, Zeiss Ultra Plus). The elemental compositions of the films were evaluated by energy dispersive X-ray spectrometry (EDX). The chemical states of the films were measured by X-ray photoelectron spectroscopy (XPS, PHI Quantera II) and the XPS penetration depth is about 10 nm. The XPS spectra were calibrated according to ref. 37 (link). During the XPS measurements, the depth profiling was performed by Ar⁺ sputtering with an etching rate of about 3.5 nm min⁻¹.

The chemical compositions and atomic scale defect states were confirmed by the XPS (Thermo ESCALAB 250, ThermoFisher Scientific, Waltham, MA, USA) and the EPR (Bruker EMXplus, X-band, Bruker, Billerica, MA, USA) measurements. The TD-SSPL and PL excited (PLE) properties were measured by a Fluorolo-3 system (HORIBA Jobin Yvon, Paris, France) in a computer-controlled Delta 9023 oven (State College, PA, USA) under various temperatures, using a 75W Xe lamp (λ_exc = 250‒800 nm) and a He‒Cd laser (λ_exc = 325 nm) as light sources. The optical band gaps (E_opt) were obtained from transmittance measurements (Shimadzu UV-3600, Shimadzu Corp., Hadano, Kanagawa, Japan). The refractive indexes (n) were measured using a spectroscopic ellipsometer (Jobin Yvon UVISEL, HORIBA Jobin Yvon, Paris, France). Both the E_opt and n of a-SiN_xO_y samples are listed in Table 1. A FLS980 (Edinburgh Instrument Ltd., Edinburgh, UK) equipped with an EPL375 pulse diode laser (λ_exc = 375 nm, pulse width ~53 ps, repetition rate ~20 MHz), and a TCSPC (resolution time ~100 ps), were used to record the time-resolved PL.