Structural modification, photoluminescence, and magnetic property enhancement with Er3

(1)

Materials Research Express

PAPER

Structural modification, photoluminescence, and magnetic property enhancement with Er 3+ doping, of sol–gel TiO 2 thin films

To cite this article: Heider Dehdouh et al 2017 Mater. Res. Express 4 086408

View the article online for updates and enhancements.

1. Introduction

The scientific and technological importance of TiO2 thin films has increased in the past few three decades, because of their interesting properties. During these decades, more attention has been focused on the optical properties to improve the TiO2 comportment. For this, doping TiO2 with trivalent rare earths seems to be of great interest in a wide variety of technological applications such as waveguiding devices [1], Bragg reflectors [2], Light-emitting devices [3], and fibers [4]. To the best of our knowledge, very few studies on the magnetic properties of TiO2 applied as diluted magnetic semiconductors (DMSs), have been implemented using the sol– gel dip-coating method.

Accordingly, the photoluminescence (PL) property of erbium (Er³⁺) as a dopant, within the TiO2 matrix, has been widely studied. Erbium (Er³⁺) is a good candidate, because of its multiple emissions in both the visible and infrared regions. On the one hand, because of its favorable infra-f transition [5]. On the other hand, as a result of its intermediate state ⁴I11/2 that has a long lifetime of 400 µs [5]. The up-conversion luminescence of Er³⁺:TiO2

as nanocrystals and thin films, under near infrared excitation, have been studied in extensive research [6–8].

Badr et al studied the up-conversion luminescence of dip-coated Er³⁺:TiO2 thin films with a laser diode of wave- length 808 nm as excitation [9]. They found that the up-converted luminescence intensity depends mainly on the erbium rate. Meng et al discovered that the use of 5% Yb³⁺ as a co-dopant can make 1% Er³⁺:TiO2 more efficient in up-conversion systems [6].

Currently, oxide-based diluted magnetic semiconductors (ODMSs) have attracted a great deal of interest, because of their ferromagnetic behavior at room temperature. Most works in TiO2 ODMS applications are focused on the transition metal-doped TiO2. As an example, elements such as Mn, Ni, Co, Cu, and Fe have an original ferromagnetism regardless of the host semiconductor material [10–15]. It is well known that the 3d transition metal elements are necessary for the origination of the magnetic state. The latter allows the application of DMS, with high Curie temperature (Tc), in the fabrication of transparent spin-based devices [16]. Further- more, the recent theoretical studies based on ab initio calculations predicted the ferromagnetic behavior with Tc H Dehdouh et al

086408

MRX

Mater. Res. Express

MRX

2053-1591

10.1088/2053-1591/aa8068

8

1 10

Materials Research Express IOP

18 August 2017

Structural modification, photoluminescence, and magnetic

property enhancement with Er ³⁺ doping, of sol–gel TiO ₂ thin films

Heider Dehdouh¹^,², Rabah Bensaha¹ and Mourad Zergoug²

1 Ceramics laboratory, Frères mentouri-Constantine-1 University, Road Ain El-Bey, 25000 Constantine, Algeria

2 Research Center in Industrial Technologies CRTI, Algiers/Thin Films development and Applications Unit (UDCMA), PO Box 64, Cheraga 16014, Sétif, Algeria

E-mail: bensaha@umc.edu.dz

Keywords: TiO2 doped Er³⁺, sol–gel, photoluminescence, magnetic properties

Abstract

Nanocrystalline undoped and Er³⁺ doped TiO2 thin ﬁlms were prepared by sol–gel dip-coating technique onto glass substrates. Post-deposited films were annealed at 450 °C for 1 h. Differential scanning calorimetric analysis showed that undoped film crystallization occurred at 339 °C, while it appears at lower temperature for Er:TiO2. X-ray diffraction and Raman spectroscopy results indicate that the films crystallize only into anatase phase, and the crystallite size decreases from 24.3 to 21.16 nm with increasing Er³⁺ doping ratio. The photoluminescence (PL) spectra are composed of two broad peaks at 520–570 nm and 640–680 nm assigned to (²H11/2, ⁴S3/2)–⁴I15/2 and

4F9/2–⁴I15/2 transitions of Er³⁺ ions, respectively. PL emission intensities increase gradually raising the erbium doping ratio. Vibrating sample magnetometer results of undoped TiO2 thin films reveal a ferromagnetic behavior at room temperature and erbium doping leads to an enhancement of the saturated magnetic moment (Ms).

PAPER

2017

RECEIVED 30 March 2017

REVISED

5 July 2017

ACCEPTED FOR PUBLICATION

18 July 2017

PUBLISHED 18 August 2017

https://doi.org/10.1088/2053-1591/aa8068 Mater. Res. Express 4 (2017) 086408