Hao Chen

Hao Chen

Researcher in complex oxide thin films, investigating defect-mediated electronic structure evolution and structure–property relationships via synchrotron-based spectroscopy and advanced methods.

Talks and presentations

FISMAT: XAS and RIXS investigation of oxygen vacancy engineering in WO3-x films: from amorphous to crystalline phases

July 08, 2025

Talk, Ca' Foscari University - Campus San Giobbe, Venice, Italy

Quantitative non-negative matrix factorization (NNMF) analysis of RIXS datasets resolves mixed-valence tungsten states (W⁴⁺, W⁵⁺, W⁶⁺) in WO3-x, enabling extraction of the previously obscured W⁵⁺ component. The results show that W⁴⁺-rich configurations dominate optical absorption and electrical conduction, with infrared response consistent with small-polaron hopping between mixed-valence sites in amorphous WO3-x.

ESRF user meeting: local structure of amorphous and crystalline WO3-x thin films studied by XANES and EXAFS

February 06, 2024

Poster, ESRF, Grenoble, France

The presence of intrinsic oxygen defects affects the local ordering and electronic structure in WO3-x. W 5d states split into two sub-bands with a dominant lower-energy component, tunable via annealing atmosphere. Changes in W–O coordination occur prior to long-range crystallization, indicating that electronic properties are governed by short-range order.

108° Congresso Nazionale: tailorable WO3-x for near-IR photonics and transparent-conductive films

September 15, 2022

Talk, Department of Physics, Università degli Studi di Milano, Milan, Italy

This work investigates WO3−x thin films prepared by RF-sputtering and annealing, demonstrating tunable structural, optical, dielectric, and electrical properties. The results highlight their potential as IR transparent conductors and their integration into 1D photonic bandgap structures, enabling surface electric field enhancement.

SPIE photonics Europe: amorphous WO3-x as transparent conductive oxide in the near-IR

April 05, 2022

Poster, Palais de la Musique et des Congrès, Strasbourg, France

RF-sputtered films exhibit smooth morphology and n-type conductivity with extended near-IR transparency. Defect engineering through post-growth annealing tunes optoelectronic properties, with low-temperature treatment optimizing performance and demonstrating strong potential compared to conventional transparent conductive films in the near-IR.

EOSAM: near-IR transparent conductive amorphous WO3-x thin layers by non-reactive RF-sputtering

September 15, 2021

Talk, Engineering Faculty, Sapienza University of Roma, Rome, Italy.

With growing demand for transparent conductive materials, this work explores amorphous WO3-x thin films as a promising alternative. Smooth, compact films were fabricated by RF-sputtering and enhanced via post-annealing, leading to improved near-IR transparency and a competitive figure of merit, highlighting their potential for next-generation optoelectronic applications.