中国物理B ›› 2025, Vol. 34 ›› Issue (6): 66302-066302.doi: 10.1088/1674-1056/adc6f3

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Laser power-induced Fermi-level shift in graphene/Al2O3 under ambient atmosphere: Toward neutralizing unintentional graphene doping

Jamal Q. M. Almarashi1, Mohamed K. Zayed1,2,†, Hesham Fares1,3,‡, Heba Sukar3, Takao Ono4, Yasushi Kanai4, and Mohamed Almokhtar3,4,§   

  1. 1 Physics Department, College of Science, Taibah University, Al-Madinah Al-Munawarah 42353, Saudi Arabia;
    2 Physics Department, Faculty of Science, Beni-Suef University, Beni-Suef 6111, Egypt;
    3 Physics Department, Assiut University, Assiut 71516, Egypt;
    4 The Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihoga-oka, Ibaraki, Osaka 567-0047, Japan
  • 收稿日期:2024-12-23 修回日期:2025-03-29 接受日期:2025-03-31 出版日期:2025-05-16 发布日期:2025-05-27
  • 通讯作者: Mohamed K. Zayed, Hesham Fares, Mohamed Almokhtar E-mail:mkzayed@outlook.com;hfhassan@taibahu.edu.sa;almoktar@aun.edu.eg
  • 基金资助:
    The authors extend their appreciation to the Deputyship for Research & Innovation, Ministry of Education in Saudi Arabia for funding this research work through the project number 445-9-687.

Laser power-induced Fermi-level shift in graphene/Al2O3 under ambient atmosphere: Toward neutralizing unintentional graphene doping

Jamal Q. M. Almarashi1, Mohamed K. Zayed1,2,†, Hesham Fares1,3,‡, Heba Sukar3, Takao Ono4, Yasushi Kanai4, and Mohamed Almokhtar3,4,§   

  1. 1 Physics Department, College of Science, Taibah University, Al-Madinah Al-Munawarah 42353, Saudi Arabia;
    2 Physics Department, Faculty of Science, Beni-Suef University, Beni-Suef 6111, Egypt;
    3 Physics Department, Assiut University, Assiut 71516, Egypt;
    4 The Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihoga-oka, Ibaraki, Osaka 567-0047, Japan
  • Received:2024-12-23 Revised:2025-03-29 Accepted:2025-03-31 Online:2025-05-16 Published:2025-05-27
  • Contact: Mohamed K. Zayed, Hesham Fares, Mohamed Almokhtar E-mail:mkzayed@outlook.com;hfhassan@taibahu.edu.sa;almoktar@aun.edu.eg
  • Supported by:
    The authors extend their appreciation to the Deputyship for Research & Innovation, Ministry of Education in Saudi Arabia for funding this research work through the project number 445-9-687.

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摘要： Manipulating unintentional doping in graphene layers, which is influenced by environmental factors and supporting substrates, is of significant concern for the performance and advancement of graphene-based devices. In this context, laser-induced tuning of charge carriers in graphene facilitates the exploration of graphene's properties in relation to its surroundings and enables laser-assisted functionalization. This has the potential to advance optoelectronic devices that utilize graphene on transparent dielectric substrates, such as Al$_{2}$O$_{3}$. In this work, laser power ($P_{\rm L}$) in Raman spectroscopy is used as a convenient contactless tool to manipulate and control unintentional carrier concentration and Fermi level position ($E_{\rm F}$) in graphene/$\alpha $-Al$_{2}$O$_{3}$ (G/Al$_{2}$O$_{3}$) under ambient conditions. Samples are annealed at 400 $^\circ$C for two hours in an ($\rm Ar+H_{2}$) atmosphere to remove any chemical residues. Analysis of the peak frequency ($\omega $) and full width at half maximum ($\varGamma $) of the G and 2D bands show that G/Al$_{2}$O$_{3}$ layers initially exhibit p-type doping, with $E_{\rm F}$ located at $\sim 100$ meV below its Dirac charge-neutral point (DCNP). Increasing $P_{\rm L}$ results in effective carrier manipulation and raises $E_{\rm F}$ above DCNP. No significant internal stress is produced due to $P_{\rm L}$, as inferred from the strain-sensitive G* band of graphene. Raman analysis of three successive cycles reveals hysteretic behavior from cycle to cycle, which is commonly reported to be limited by the type and density of the existing unintentional doping. Because of the ubiquitous nature of unintentional doping in graphene, manipulating it using contactless laser power to realize the desired graphene properties would be one of the best available practical approaches.

关键词: graphene, Raman spectroscopy, laser power, unintentional graphene doping, ambient conditions, optoelectronics

Abstract: Manipulating unintentional doping in graphene layers, which is influenced by environmental factors and supporting substrates, is of significant concern for the performance and advancement of graphene-based devices. In this context, laser-induced tuning of charge carriers in graphene facilitates the exploration of graphene's properties in relation to its surroundings and enables laser-assisted functionalization. This has the potential to advance optoelectronic devices that utilize graphene on transparent dielectric substrates, such as Al$_{2}$O$_{3}$. In this work, laser power ($P_{\rm L}$) in Raman spectroscopy is used as a convenient contactless tool to manipulate and control unintentional carrier concentration and Fermi level position ($E_{\rm F}$) in graphene/$\alpha $-Al$_{2}$O$_{3}$ (G/Al$_{2}$O$_{3}$) under ambient conditions. Samples are annealed at 400 $^\circ$C for two hours in an ($\rm Ar+H_{2}$) atmosphere to remove any chemical residues. Analysis of the peak frequency ($\omega $) and full width at half maximum ($\varGamma $) of the G and 2D bands show that G/Al$_{2}$O$_{3}$ layers initially exhibit p-type doping, with $E_{\rm F}$ located at $\sim 100$ meV below its Dirac charge-neutral point (DCNP). Increasing $P_{\rm L}$ results in effective carrier manipulation and raises $E_{\rm F}$ above DCNP. No significant internal stress is produced due to $P_{\rm L}$, as inferred from the strain-sensitive G* band of graphene. Raman analysis of three successive cycles reveals hysteretic behavior from cycle to cycle, which is commonly reported to be limited by the type and density of the existing unintentional doping. Because of the ubiquitous nature of unintentional doping in graphene, manipulating it using contactless laser power to realize the desired graphene properties would be one of the best available practical approaches.

Key words: graphene, Raman spectroscopy, laser power, unintentional graphene doping, ambient conditions, optoelectronics

中图分类号:  (Phonons in graphene)

  • 63.22.Rc
68.65.Pq (Graphene films) 72.80.Vp (Electronic transport in graphene) 78.67.Wj (Optical properties of graphene)