Efficient energy transfer in Eu-doped ZnO on diamond film

Abstract

Eu-zinc oxide (ZnO) has been fabricated on a p-diamond substrate by a hydrothermal technique. Efficient Eu-ZnO/diamond visible light emission is observed in the electroluminescence process. The mechanism for the energy transfer behavior and the emissions is discussed.Semiconductors doped with rare earth (RE) elements have attracted much attention in recent years due to their novel optical properties and promising applications in many elds, such as ber ampliers, light emitting devices and uorescent lamps. 1-4 In most of these applications, efficient energy transfer from the host to the RE 3+ is desired. ZnO with a band gap of 3.37 eV and a bound exciton energy of 60 meV is also an important semiconductor for which UV and visible emissions are widely reported. 5 Unfortunately, the work of harvesting intense Eu 3+ emission from ZnO lms, ceramics, and powders remains disappointing because of the strong quenching effect of the wide-band, self-activated, green or yellow emissions and the higher energy-level position of Eu 3+ relative to the bottom conduction band (CB). 6 It has been established that direct ZnO / Eu 3+ energy transfer seems physically impossible, as the radiative and nonradiative decay of excitons in ZnO are >10 2 times faster than the energy-transfer rate of RE 3+ . Fortunately, energy transfer can be facilitated by the presence of intrinsic or extrinsic defects as energy trap centers in various systems, such as ZnO/diamond, 7 which suggests that the introduction of an appropriate trap center is crucial for efficient ZnO / Eu 3+ energy transfer. Several groups have reported that defects, either intrinsic or extrinsic, can serve as the energy trapping centers to facilitate energy transfer and relevant light emission. Park et al. indicated that extrinsic defects like chlorine impurities can assist the red emission in Eu 3+ -doped ZnO. 8 Wang et al. reported the surface defects may act to help the process of energy transfer from ZnO to Eu 3+ ions. 9 Zeng et al. indicated that in Eu-doped ZnO microspheres Eu 2+ ions act as the trapping centers and transfer energy to Eu 3+ ions, leading to the emission. 10In this work, nanostructural Eu doped n-ZnO on p-type diamond has been fabricated to research the current-voltage (I-V), electroluminescence (EL) and photoluminescence (PL) properties. For the rst time, efficient Eu-ZnO/diamond visible light emission was observed. The Eu-ZnO/diamond has been realized with good rectifying behavior. By rst-principles calculation, it is demonstrated that the doped Eu atoms are favorable to the octahedral interstice in ZnO lattice.The polycrystalline diamond lm is deposited on Si wafer by hot lament CVD system. 11 Boron source of diborane or trimethylborate was additionally introduced to the reaction gases of methane/hydrogen (CH 4 /H 2 ). Before the hydrothermal process, a ZnO seed layer was deposited by radio frequency (at 13.56 MHz) magnetron sputtering process. For the hydrothermal growth, the aqueous solution of zinc acetate dihydrate and hexamethylenetetramine ...

Red luminescence and UV light generation of europium doped zinc oxide thin films for optoelectronic applications

“…This is explained by the fact that these carriers trapped in oxygen vacancies could transfer their energy to the Eu 3+ ions via an energy transfer process. Similar energy transfer behaviour is observed in other studies [48][49][50]. Subsequently, we observe the radiative transitions from 5 D to 7 F as shown in Figure 7.…”

Strong near band edge emission of (Ce, Yb) co-doped ZnO thin films after high temperature annealing

“…On the other hand, acquiring intense ultraviolet (UV) emission from ZnO is always a challenge in ZnO based UV photonics and various methods to enhance the UV emission have been reported [13][14][15][16]. REs doping of ZnO and its influence on the near band edge (NBE) emission of ZnO [17,18] were reported, and a NBE enhancement was observed but the mechanism for the enhancement is not clear. Ce 3+ can emit blue light and the absorption cross section of the electric-dipole allowed 4f-5d transition is large (of the order of 10 −18 cm 2 ), while the radiation from Yb 3+ (~980 nm) has many important applications.…”

Doping of RE ions in the 2D ZnO layered system to achieve low-dimensional upconverted persistent luminescence based on asymmetric doping in ZnO systems

“…This corresponds to the experimental report that stated that the existence of Eu 3+ in ZnO is actually responsible for the red luminescence. 107,108 Meanwhile, the higher energy emission at 590 nm (2.1 eV), which was reported experimentally, 35 that neighbors the Eu-intrinsic de-excitation at 615-650 nm is rather low and could be viewed as having zero oscillator strength, as shown in Fig. 12(e).…”