This study explores the enhancement of piezoelectric properties in zinc oxide (ZnO)-based thin films through gallium (Ga) ion doping using various fabrication processes. Three distinct doping methods and two doping concentrations (1% and 3%) were systematically investigated. Experimental results reveal that Ga-doped ZnO (GZO) films exhibit reduced electrical resistivity, increased optical transmittance, and wider bandgaps compared to undoped ZnO films. Among the examined conditions, GZO films with 1% Ga3⁺ doping achieved the lowest resistivity of 0.0065 Ω·cm and the highest piezoelectric output of 1098.83 mW. In contrast, excessive Ga3⁺ doping at 3% led to increased lattice defects, inducing internal stress and electric field screening effects that diminished the piezoelectric performance. Durability assessments further confirmed the mechanical robustness and long-term stability of GZO devices under sustained vibrational loading. These findings underscore the effectiveness of Ga³⁺ doping in enhancing the piezoelectric performance of ZnO thin films and highlight their potential for applications in energy harvesting technologies.
SaleemSJameelMHRehmanA, et al.Evaluation of structural, morphological, optical, and electrical properties of zinc oxide semiconductor nanoparticles with microwave plasma treatment for electronic device applications. J Mater Res Technol2022; 19: 2126–2134.
2.
UpadhayaDPurkayasthaDD. Enhanced wettability and photocatalytic activity of seed layer assisted one dimensional ZnO nanorods synthesized by hydrothermal method. Ceram Int2020; 46: 15831–15839.
3.
Al-She'ireyAYBalouchAMawarnisER, et al.Effect of ZnO seed layer annealing temperature on the growth of ZnO nanorods and its catalytic application. Opt Mater2022; 131: 112652.
4.
ColmenaresYNCorrerWLimaBS, et al.The effect of morphology on the ozone-gas sensing properties of zinc oxide sputtered films. Thin Solid Films2020; 703: 137975.
5.
YuLYuanZWangB, et al.Hydrothermal growth of single-crystalline Ga-doped ZnO microrods for ultraviolet detection. Micro Nanostructures2022; 166: 207214.
6.
ZhaoMHWangZLMaoSX. Piezoelectric characterization of individual zinc oxide nanobelt probed by piezoresponse force microscope. Nano Lett2004; 4: 587–590.
7.
KumarVSinghSKSharmaH, et al.Investigation of structural and optical properties of ZnO thin films of different thickness grown by pulsed laser deposition method. Phys B: Condens Matter2019; 552: 221–226.
8.
MaSKitaiAH. Chemical vapor deposition-based growth of aligned ZnO nanowires on polycrystalline Zn2GeO4: mn substrates. J Mater Sci2017; 52: 9324–9334.
9.
KhanMIBhattiKAQindeelR, et al.Characterizations of multilayer ZnO thin films deposited by sol-gel spin coating technique. Results Phys2017; 7: 651–655.
10.
WonglakhonTZahnD. Interaction potentials for modelling GaN precipitation and solid state polymorphism. J Phys Condens Matter2020; 32: 205401.
11.
DuDMaXAnW, et al.Flexible piezoresistive pressure sensor based on wrinkled layers with fast response for wearable applications. Measurement ( Mahwah N J)2022; 201: 111645.
12.
RakhshaAAbdizadehHPourshabanE, et al.Controlling the performance of one-dimensional homojunction UV detectors based on ZnO nanoneedles array. Sens Actuators A: Phys2021; 331: 112916.
13.
AleksandrovaM. Polymeric seed layer as a simple approach for nanostructuring of Ga-doped ZnO films for flexible piezoelectric energy harvesting. Microelectron Eng2020; 233: 111434.
14.
TahaIAbdulhamidZMStraubingerR, et al.Ga-doped ZnO nanoparticles for enhanced CO2 gas sensing applications. Sci Rep2024; 14: 29712.
15.
IslamMRRahmanMFarhadSFU, et al.Structural, optical and photocatalysis properties of sol-gel deposited Al-doped ZnO thin films. Surf Interfaces2019; 16: 120–126.
16.
YangJJiangYLiL, et al.Structural, morphological, optical and electrical properties of Ga-doped ZnO transparent conducting thin films. Appl Surf Sci2017; 421: 446–452.
17.
LemineASBhadraJSadasivuniKK, et al.3D Printing flexible Ga-doped ZnO films for wearable energy harvesting: thermoelectric and piezoelectric nanogenerators. J Mater Sci: Mater Electron2024; 35: 1639.
18.
LeeJHKumarBLeeKY, et al.Synthesis of Ga-doped ZnO nanorods using an aqueous solution method for a piezoelectric nanogenerator. J Nanosci Nanotechnol2012; 12: 3430–3433.
19.
ThanhBDAndreyNPavelO, et al.Multilevel modeling of 1-3 piezoelectric energy harvester based on porous piezoceramics. J Appl Comput Mech2023; 9: 763–774.
20.
MotlanSiregarNPanggabeanJH. The effect of spin coating speed on structural and optical properties of ZnO and ZnO/Dye thin films synthesized by Sol-Gel spin coating method. J Phys: Conf Ser2021; 1819: 012050.
21.
LeATAhmadipourMPungSY. A review on ZnO-based piezoelectric nanogenerators: synthesis, characterization techniques, performance enhancement and applications. J Alloys Compd2020; 844: 156172.
22.
AichaSLJollyBKishorKS, et al.3D Printing flexible Ga-doped ZnO films for wearable energy harvesting: thermoelectric and piezoelectric nanogenerators. J Mater Sci Mater Electron2024; 35: 1639.
23.
SanazAMohammadMMortezaSG. Thin Ga-doped ZnO film with enhanced dual visible lines emission. Current Nanomaterials2024; 9: P279–P285.
24.
YangCCSuYKHsiaoCH, et al.Low-Frequency noise characteristics of gallium-doped ZnO nanosheets as photodetectors. J Electrochem Soc2014; 161: H399–H403.
25.
MuchuweniESathiarajTSNyakotyoH. Effect of gallium doping on the structural, optical and electrical properties of zinc oxide thin films prepared by spray pyrolysis. Ceram Int2016; 42: 10066–10070.
26.
LotusAFKangYCWalkerJI, et al.Effect of aluminum oxide doping on the structural, electrical, and optical properties of zinc oxide (AOZO) nanofibers synthesized by electrospinning. Mater Sci Eng B2010; 166: 61–66.
27.
SoaramKGiwoongNHyunggilP, et al.Effects of doping with Al, Ga, and in on structural and optical properties of ZnO nanorods grown by hydrothermal method. Bull Korean Chem Soc2013; 34: 1205.
28.
WangXHuangXWongZM, et al.Gallium-Doped zinc oxide nanostructures for tunable transparent thermoelectric films. ACS Appl Nano Mater2022; 5: 8631–8639.
29.
ChenSWarwickMEABinionsR. Effects of film thickness and thermal treatment on the structural and opto-electronic properties of Ga-doped ZnO films deposited by sol–gel method. Sol. Energy mater Sol cells2015; 137: 202–209.
30.
KuprenaiteSAbrutisAKubiliusV, et al.Effects of annealing conditions and film thickness on electrical and optical properties of epitaxial Al-doped ZnO films. Thin Solid Films2016; 599: 19–26.
31.
MuivaCMSathiarajTSMaabongK. Effect of doping concentration on the properties of aluminium doped zinc oxide thin films prepared by spray pyrolysis for transparent electrode applications. Ceram Int2011; 37: 555–560.
32.
PerumalRLakshmananSJihHL. Substrate and doping effects on the growth aspects of Zinc oxide thin films developed on a GaN substrate by the sputtering technique. Processes2025; 13: 1257.
33.
YuCFChenSHSunSJ, et al.Influence of the grain boundary barrier height on the electrical properties of gallium doped ZnO thin films. Appl Surf Sci2011; 257: 6498–6502.
34.
ChengJPZhangXBLuoZQ. Oriented growth of ZnO nanostructures on Si and Al substrates. Surf Coat Technol2008; 202: 4681–4686.
35.
JiangSZhaoXZhangJ, et al.Metal-doped functional zinc oxide nanosheets as flexible piezoelectric generator for self-powered mechanical sensing. Sens Actuators A: Phys2024; 371: 115337.
36.
ChengLCBrahmaSHuangJL, et al.Enhanced piezoelectric coefficient and the piezoelectric nanogenerator output performance in Y-doped ZnO thin films. Mater Sci Semicond Process2022; 146: 106703.
37.
LookDC. Recent advances in ZnO materials and devices. Mater Sci Eng B2001; 80: 383–387.
38.
ChenWYJengJSHuangKL, et al.Modulation of Ni valence in p-type NiO films via substitution of Ni by Cu. J Vac Sci Technol A2013; 31: 021501.
39.
JengJS. Improvement of transistor characteristics and stability for solution-processed ultra-thin high-valence niobium doped zinc-tin oxide thin film transistors. J Alloys Compd2016; 676: 86–90.
40.
PandeyRKDuttaJBrahmaS, et al.Review on ZnO-based piezotronics and piezoelectric nanogenerators: aspects of piezopotential and screening effect. J Phys Mater2021; 4: 044011.
41.
MinarMMoelansN. Influence of surface energy anisotropy on nucleation and crystallographic texture of polycrystalline deposits. Comput Mater Sci2024; 231: 112575.
42.
LiuF. Nucleation/growth design by thermo-kinetic partition. J Mater Sci Technol2023; 155: 72–81.
43.
AndersonJ. Fundamentals of zinc oxide as a semiconductor. Rep Prog Phys2009; 72: 126501.
44.
SapnaDPSanjayanSIvanPP, et al.Highly conductive and transparent gallium doped zinc oxide thin films via chemical vapor deposition. Sci Rep2020; 10: 38.
45.
TielemannCReinschSMaabR, et al.Internal nucleation tendency and crystal surface energy obtained from bond energies and crystal lattice data. J Non-Cryst Solids: X2022; 14: 100093.
46.
LatychevskaiaTCassidyCShintakeT. Bragg holography of nano-crystals. Ultramicroscopy2021; 230: 113376.
47.
SunCZhongCWangL, et al.Study on suppression of transverse mechanical coupling of rectangular double-laminated bending vibration elements. Crystals (Basel)2022; 12: 1737.
48.
AbderrahimMNavpreetKNicolaP, et al.One dimensional ZnO nanostructures: growth and chemical sensing performances. Nanomaterials2020; 10: 1940.
49.
HallajzadehAMAbdizadehHTaheriM, et al.Hierarchical porous ga doped ZnO films synthesized by sol-electrophoretic deposition. Ceram Int2020; 46: 12665–12674.
50.
MingyanXFangpeiLWenboP, et al.Pyro-Phototronic effect enhanced MXene/ZnO heterojunction nanogenerator for light energy harvesting. Nanoenergy Adv2023; 3: 401–420.
