Influence of substrate temperature on graphene oxide thin films synthesis by laser ablation technique

Abstract

In this paper, we studied the influence of the substrate temperature (Ts) on the deposition of carbon thin films by the pulsed laser deposition technique. Thin films were synthesized using a highly oriented pyrolytic graphite target, which was irradiated by the fundamental harmonic (1064 nm) of a Nd:YAG pulsed laser. In the experimental conditions, the Ts varied from room temperature to 500 °C, the gas pressure (oxygen, 50 mTorr) remained the same for all samples, and the ablation time was 5 min for each thin film. The samples were characterized by x-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy in conjunction with energy dispersive x-ray spectroscopy, atomic force microscopy, and contact angle measurement. The characterization results allowed us to determine that the thin films deposited on silicon substrates at 400 and 500 °C (samples S1 and S2) were multilayers graphene oxide. From XRD, Raman spectroscopy, and FTIR results, we concluded that the degree of oxidation and graphitization of the carbon thin films were influenced by the Ts. Additionally, the contact angle measurement showed that for samples S1 and S2, the contact angle was greater than 94°, and for samples S3 and S4 (amorphous carbon), it was less than 62°.

Pulsed Laser Deposition of Carbon-Based Materials: A Focused Review of Methods and Results

“…The latter behavior is often observed at low substrate temperatures and is associated with higher density of defects and an increasingly amorphous character, as evidenced by various microscopy techniques and Raman spectroscopy (see, for example, [123,125,127,130].…”

“…Two main approaches have been tested for PLD of graphene: one that involves the use of metallic catalysts deposited on the substrate in different phases of the film growth, and one that proceeds without catalysts. The latter approach is particularly attractive as it eliminates the need to transfer the deposited graphene film and to grow it, in principle, directly on any desired substrate (e.g., pure and doped Si, SiO 2 and fused silica [121][122][123][124][125][126][127][128][129], sapphire [130], copper [131][132][133], glass [134]). In fact, considerations such as substrate-film lattice mismatch and film-substrate adhesion should, as usual with thin-film deposition techniques, always be considered when producing usable films for specific applications is the goal.…”

“…In general, introducing a background gas and tailoring its composition proved a very efficient strategy for the room-temperature deposition of graphene and graphene oxide [125,133], as will be discussed in more detail in Section 4.3.…”

“…The amount of incorporated dopant can be tailored either by controlling the pressure of the gas, in cases when the deposition is carried out in a gaseous atmosphere containing the desired dopant, or by controlling the ablation time and stoichiometry of the dopantcontaining target. Multilayer graphene oxide [125] and hydrogenated graphene [123] have been grown catalyst-free by using, respectively, oxygen and hydrocarbons (e.g., CH 4 ) as background gases. Both works studied the effect of substrate temperature on the deposited films while keeping all other experimental parameters constant and confirmed that, at low temperatures, the deposited material tends to be an amorphous mixture of sp 2 /sp 3 -C rather than graphenic in nature.…”

“…Both works studied the effect of substrate temperature on the deposited films while keeping all other experimental parameters constant and confirmed that, at low temperatures, the deposited material tends to be an amorphous mixture of sp 2 /sp 3 -C rather than graphenic in nature. In [125], graphene oxide was produced only at substrate temperatures of 400 • C and higher, while lower temperatures promoted the formation of amorphous C films with lower crystallinity and different wettability behavior (hydrophilic as opposed to the usual hydrophobic character of graphene oxide). Similarly, in [123], when the substrate temperature was increased from room temperature to 400 • C, a transition took place from amorphous hydrogenated C films to a hydrogenated graphene structure, while a further temperature increase caused film dehydrogenation and a higher number of defects.…”