Characteristics of Field Emitters on the Basis of Pd-Adsorbed ZnO Nanostructures by Photochemical Method

Abstract

In this investigation, field electron emission (FE) performances of pure zinc oxide (ZnO) nanorod (NR) arrays and ZnO NRs with adsorbed palladium nanoparticles (Pd-ZnO) were explored under high-vacuum conditions. The nanostructures were successfully grown on substrates via a simple hydrothermal method (HM) and photochemical synthesis process. After characterizing the structural and crystal results of the as-grown samples, it was found that all NR structures were observed to be single crystals and presented structurally uniformity with the hexagonal wurtzite structures. Also, photoluminescence measurement was used to realize the optical properties of all samples. The results showed that pure ZnO and Pd-ZnO nanostructures exhibited two different emissions: one is an ultraviolet emission in the short wavelength and the other is green emissions. As for the field emitter performance, adsorbing with Pd nanoparticles reduced the turn-on field from 6.6 to 6.4 V/μm. The field enhancement factors (β) of pure ZnO (FE1) and Pd-ZnO NRs (FE2) were 2546 and 5947, respectively. The results revealed that the Pd-ZnO samples exhibited enhanced FE performances, which revealed the use of Pd-ZnO nanostructures as promising emitters for FE-based devices.

High Sensitivity of Extended-Gate Field-Effect Transistors Based on 1-D ZnO:Ag Nanomaterials through a Cheap Photochemical Synthesis as pH Sensors at Room Temperature

“…In other words, a large number of OH – ions cause an additional negative bias on the gate; thus, the I DS decreases when the pH value increases. − When the I DS was 0.3 mA, the voltage sensitivity and linearity of the Z@Ag-0 nanostructures were 24.77 mV/pH and 0.975, respectively, and the voltage sensitivity and linearity of the Z@Ag-1 nanostructures were 59.06 mV/pH and 0.996, respectively, as shown in Figure g,h. Based on the above results, it can be found that the ZnO pH sensor decorated with Ag NPs has good electrical properties and pH-sensing performances, which suggests that the density of Ag NPs can create more surface-active sites for H + or OH – sensing. − That is to say, the Ag NPs can transmit sensing signals more easily; this phenomenon is similar to a previous report . The V T,EGFET could be defined and expressed as the following equation − V normalT , E G F E T = V normalT , M O S F E T − φ M / q − E normalR normalE normalF + χ normalS normalo normall − ψ where V T,MOSFET is the threshold voltage of the MOSFET, φ M is the metal gate work function of the reference electrode, q is the electron charge, E REF is the potential of the reference, χ Sol is the surface dipole potential of the electrolytic solution, and ψ is the surface potential between the interface of the pH buffer solution and the sensing material.…”

Significant enhancement in the cold emission characteristics of chemically synthesized super-hydrophobic zinc oxide rods by nickel doping

“…Young and Y. L. Chu developed a system of Pd nanoparticle decorated ZnO quantum dots and quantum wires. 34 In their case, including Pd did not have a marked effect in changing the turnon eld, but the decorated system showed more than a 100% increase in the enhancement factor. Jun Chen obtained a very high emission current of 20 mA et al from their developed system of indium-doped ZnO.…”

“… 31 Though this has fundamental importance, it lacks practical application. The work in 34 showed that including Pd did not affect the emission characteristics much. Though doped ZnO gives a very interesting and useful FE result, it has the same drawback with a high thermal energy required in the synthesis process.…”