Surface Oxide Effect on Optical Sensing and Photoelectric Conversion of α-In₂Se₃ Hexagonal Microplates

Abstract

The surface formation oxide assists of visible to ultraviolet photoelectric conversion in α-In2Se3 hexagonal microplates has been explored. Hexagonal α-In2Se3 microplates with the sizes of 10s to 100s of micrometers were synthesized and prepared by the chemical vapor transport method using ICl3 as a transport agent. Many vacancies and surface imperfection states have been found in the bulk and on the surface of the microplate because of the intrinsic defect nature of α-In2Se3. To discover physical and chemical properties and finding technological uses of α-In2Se3, several experiments including transmission electron miscopy (TEM), X-ray photoelectron spectroscopy (XPS), surface photovoltage (SPV), photoluminescence (PL), surface photoresponse (SPR), photoconductivity (PC), and thermoreflectance (TR) measurements have been carried out. Experimental results of TEM, XPS, SPV, PL, and SPR measurements show that a surface oxidation layer α-In2Se3-3xO3x (0 ≤ x ≤ 1) has formed on the crystal face of α-In2Se3 in environmental air with the inner layer content close to In2Se3 but the outermost layer content approaching In2O3. The near band edge transitions of α-In2Se3 microplates have been probed experimentally by TR and PC measurements. The direct band gap of α-In2Se3 has been determined to be 1.453 eV. The SPV result shows a maximum quantum efficiency of the surface oxide α-In2Se3-3xO3x (0 ≤ x ≤ 1) that presents a peak photoresponse near 2.18 eV. The analyses of SPV, SPR, PL, TR, and PC measurements revealed that the surface oxide layer facilitates the conversion of the ultraviolet to the visible range while the native defects (Se and In vacancies) sustain photoconductivity in the near-infrared region. On the basis of the experimental results a wide-energy-range photodetector that combines PC- and SPR-mode operations for α-In2Se3 microplate has been made. The testing results show a well-behaved function of photoelectric conversion in the near-infrared to ultraviolet region via the auxiliary forming of surface oxide on the crystalline face of the α-In2Se3 microplates.

Engineering p – n junctions and bandgap tuning of InSe nanolayers by controlled oxidation

“…On the other hand, as for silicon, the existence of stable oxides at room temperature can offer prospects for novel applications [22,23]. Thermal annealing of bulk In-Se compounds in air or in an oxygen-rich environment can produce native oxides [24][25][26][27]. The formation and control of such oxides in 2D flakes has not yet been examined and can offer opportunities to fabricate novel 2D hybrid heterostructures.…”

Atomic Layer Growth of InSe and Sb2Se3 Layered Semiconductors and Their Heterostructure

“…One of the reasons for this attenuation has been attributed to direct-to-indirect bandgap crossover, while another explanation has been attributed to the enhancement of non-radiative recombination processes in the thin flakes [15,16]. To date, InSe films have been produced mostly via chemical vapor deposition (CVD), sputtering, exfoliation, and electrodeposition [15,[17][18][19][20]. In these cases, the films are either small, on the order of a few tens of micrometers per side (exfoliation) or are composed of flakes or platelets.…”

Optical-memory switching and oxygen detection based on the CVT grown γ- and α-phase In2Se3

“…The ␣ and ␥ modifications are two most stable phases of diindium triselenide stabilized at room temperature. Diindium triselenides of ␣ and ␥ phases are suitable for application in solar-cell material [3], nanostructural phase-change memory [4,5], wide-energy-range photodetector [6,7], and thickness-tunable long pass filter [8]. The diversified crystal phases and various applications of In 2 Se 3 are attributed to the misvalency of In III and Se VI atoms in the indium chalcogenide to form different crystalline and amorphous states [9] as well as diversified crystal phases and lattice forms [10,11].…”

“…The diversified crystal phases and various applications of In 2 Se 3 are attributed to the misvalency of In III and Se VI atoms in the indium chalcogenide to form different crystalline and amorphous states [9] as well as diversified crystal phases and lattice forms [10,11]. Recently the individual study on respective ␣-In 2 Se 3 or ␥-In 2 Se 3 has been implemented [6,8]. The surface of ␣-In 2 Se 3 was been proven to contain oxide composition.…”