Faridawati 

Department of Physics, Faculty of Science and Data Analytics, Institut Teknologi Sepuluh Nopember (ITS), Kampus ITS, Sukolilo, Surabaya 60111, Indonesia

Sudarsono

Department of Physics, Faculty of Science and Data Analytics, Institut Teknologi Sepuluh Nopember (ITS), Kampus ITS, Sukolilo, Surabaya 60111, Indonesia

Nurrisma Puspitasari

Department of Physics, Faculty of Science and Data Analytics, Institut Teknologi Sepuluh Nopember (ITS), Kampus ITS, Sukolilo, Surabaya 60111, Indonesia

Arief Bustomi

Department of Physics, Faculty of Science and Data Analytics, Institut Teknologi Sepuluh Nopember (ITS), Kampus ITS, Sukolilo, Surabaya 60111, Indonesia

Ali Yunus Rohedi

Department of Physics, Faculty of Science and Data Analytics, Institut Teknologi Sepuluh Nopember (ITS), Kampus ITS, Sukolilo, Surabaya 60111, Indonesia

Gontjang Prajitno

Department of Physics, Faculty of Science and Data Analytics, Institut Teknologi Sepuluh Nopember (ITS), Kampus ITS, Sukolilo, Surabaya 60111, Indonesia

Eko Minarto

Department of Physics, Faculty of Science and Data Analytics, Institut Teknologi Sepuluh Nopember (ITS), Kampus ITS, Sukolilo, Surabaya 60111, Indonesia

Yono Hadi Pramono

Department of Physics, Faculty of Science and Data Analytics, Institut Teknologi Sepuluh Nopember (ITS), Kampus ITS, Sukolilo, Surabaya 60111, Indonesia

Gatut Yudoyono

Department of Physics, Faculty of Science and Data Analytics, Institut Teknologi Sepuluh Nopember (ITS), Kampus ITS, Sukolilo, Surabaya 60111, Indonesia

DOI: https://doi.org/10.19184/cerimre.v8i2.53700

ABSTRACT 

We report the temperature-dependent optical properties of reduced graphene oxide (rGO)/MgF₂ films, emphasizing the emergence of multi-band gap transitions and sub-band gap states for optoelectronic applications. rGO films were thermally annealed at varying temperatures (400°C and 800°C), and their optical response was analyzed using UV-VIS spectroscopy. As deposited rGO film with an annealed temperature of 400°C exhibited a single dominant band gap transition at 2.07 eV, characteristic of π–π* transitions. Upon annealing at 800°C, additional transitions appeared at 2.34 eV until 2.40 eV, indicating the development of multi-band gap behavior due to structural ordering, oxygen functional group removal, and the formation of localized defect states. The calculated Urbach energy (𝐸𝑢 ) increased from 0.279 eV to 0.288 eV at 800°C, signifying increased disorder and sharper optical absorption edges. The synergistic effects of rGO’s tunable band structure and MgF₂’s dielectric properties offer a versatile platform for optoelectronic devices application, such as broadband photodetectors, multi-junction solar cells and plasmon-enhanced sensors.

Keywords: Multi-band gap, Sub-band gap, Plasmonic, optoelectronic.