Effect of ZnO Buffer Layer on the Structural and Optical Properties of Zn[sub 2]GeO[sub 4]:Mn[sup 2+] Thin Films

Abstract

Mn 2+ -activated Zn 2 GeO 4 phosphor thin films were deposited on quartz substrates using the radio frequency magnetron sputtering technique. The crystallanity, composition ratio, and luminescent behavior of the films were highly sensitive to the deposition parameters. Zn 2 GeO 4 :Mn 2+ films grown on amorphous substrates were polycrystalline in nature, whereas those deposited on the ZnO buffer layer were highly oriented along the ͑220͒ plane under similar deposition conditions. Tauc plot analysis of the Zn 2 GeO 4 :Mn 2+ films grown on ZnO/quartz substrate exhibits strong subband absorption in comparison to the Zn 2 GeO 4 :Mn 2+ film deposited on quartz substrate. The spectral overlap between the subband states and excited levels of Mn 2+ is more favored with the buffer layer presence improving the resonant energy transfer from the host to the activator. The subsequent 4 T 1 -6 A 1 transition in the Mn 2+ levels results in the green photoluminescent ͑PL͒ emission at 540 nm. The maximum PL emission is observed for the film deposited at 650°C. The photoluminescent excitation spectra of Zn 2 GeO 4 :Mn 2+ film on ZnO/quartz substrate showed a blueshift with substrate temperature.

Control of Interfacial Structure with Precursor Chemistry in Radial Core/Shell Nanowires of Zinc Oxide, Optically-Active Erbium, and Germanium

“…The ZnO UV/visible spectrum of ZnO/Er/GeNWs with a ZnO surface coating grown by a PVD process (the black trace in Figure ) exhibits a ZnO near-band-edge (NBE) ultraviolet emission at 3.30 eV (375 nm) and a deep-level trap feature at 2.25 eV (550 nm), whereas the GeNWs with a surface modified by a CVD process (the gray trace in Figure ) pointedly lack the ZnO NBE featuresonly a weak broad emission in the 2.4−2.9 eV range; this latter spectrum (gray trace) is consistent with the blue-green emission of Zn 2 GeO 4 . , Such PL spectral differences are consistent with the different phases and architectures of each type of nanowire, as shown by TEM/EDX data.…”

Electroluminescent characteristics of ZnGa2O4:Dy3+ thin film devices fabricated on glass substrates

“…Reducing the defect density by high temperature post‐annealing processes was, however, tedious due to low softening temperature of the glass substrate. So, based on earlier reports 23–27, it was checked whether any improvement in device output could be accomplished by depositing an interfacial layer of ZnO in between the active layer and the amorphous‐like substrate.…”

Crystallographic Alignment of ZnO Nanorod Arrays on Zn2GeO4 Nanocrystals: Promising Lattice-Matched Substrates

“…3,11 In this report, we show that the novel ternary Zn 2 GeO 4 crystals can be used as lattice-matched substrates for ZnO nanorod array growth. Due to the difficulty in obtaining Zn 2 GeO 4 bulk substrates or thin films with uniform crystal structure, 12,13 the single-crystalline Zn 2 GeO 4 nanowires can be used as ideal substrates for nanorod array growth and crystallographic investigations. 14 While the insulating substrates (such as Al 2 O 3 and MgO) would inhibit their applications, nanoheterojunction devices based on ZnO nanowire array grown on semiconductingGaNsubstratehavebeendemonstratedrecently.…”

“…15,16 Zn 2 GeO 4 is a wide-band-gap semiconductor (E g ) 4.68 eV) with tunable optical properties. 12,13 It is believed that Zn 2 GeO 4 crystals not only serve as substrates for epitaxial ZnO nanowire array growth but also can be integrated into future nanoscale electronic and optoelectronic heterojunction devices.…”

“…In this report, we show that the novel ternary Zn 2 GeO 4 crystals can be used as lattice-matched substrates for ZnO nanorod array growth. Due to the difficulty in obtaining Zn 2 GeO 4 bulk substrates or thin films with uniform crystal structure, , the single-crystalline Zn 2 GeO 4 nanowires can be used as ideal substrates for nanorod array growth and crystallographic investigations . While the insulating substrates (such as Al 2 O 3 and MgO) would inhibit their applications, nanoheterojunction devices based on ZnO nanowire array grown on semiconducting GaN substrate have been demonstrated recently. , Zn 2 GeO 4 is a wide-band-gap semiconductor ( E g = 4.68 eV) with tunable optical properties. , It is believed that Zn 2 GeO 4 crystals not only serve as substrates for epitaxial ZnO nanowire array growth but also can be integrated into future nanoscale electronic and optoelectronic heterojunction devices.…”