Electrical conductivity and photoresistance of atomic layer deposited Al-doped ZnO films

Abstract

Al-doped ZnO films were deposited by the atomic layer deposition (ALD) on both glass and sapphire (0001) substrates. The Al composition of the films was varied by controlling the Zn:Al pulse cycle ratios. The films were characterized by the atomic force microscopy, x-ray photoelectron spectroscopy, x-ray diffraction, and optical measurements. The Film resistivity was measured as a function of Zn:Al cycle ratios as well as temperature for films grown at various substrate temperature used for ALD deposition. The resistivity of the ALD grown films decreases significantly, and so as the increase in the carrier concentration as the cycle ratio increases. The systematic measurements of temperature dependence of resistivity of films at various cycle ratios clearly demonstrate the crossover of the metal–semiconductor–insulator phase with the function of temperature as well as the cycle ratios. The average transmission of all films is greater than 85% and the optical absorption increases significantly in the visible region as the cycle ratio increases. The authors observed a remarkable dependence of photoresistance on electrical conductivity for ALD-grown films with varying cycle ratios, which control the Al content in the film. Our results suggest that Al3+ ions are incorporated as substitutional or interstitial sites of the ZnO matrix. However, an addition of an excessive amount of Al content causes the formation of Al2O3 and related clusters as carrier traps opposed to electron donors, resulting in an increase in the resistivity and other associated phenomena.

Extreme tunability in aluminum doped Zinc Oxide plasmonic materials for near-infrared applications

“…The Al-doped ZnO (AZO) thin films with varying thickness and multilayers comprising of different Al:Zn composition ratios were grown via alternate deposition of diethyl zinc (DEZ, Zn(C 2 H 5 ) 2 ), H 2 O and trimethylaluminum (TMA, Al(CH 3 ) 3 ) through atomic layer deposition (ALD) cycles 22 (see supplementary information ). ALD is used to attain conformal and pinhole-free films with a high degree of thickness control.…”

Electro-thermal control of aluminum-doped zinc oxide/vanadium dioxide multilayered thin films for smart-device applications

“…Therefore, a thick film of Al:ZnO, which has unique transparent heater qualities 29 , was grown on top of the VO 2 thin films using atomic layer deposition (ALD). Details on these Al:ZnO films can be found in the literature 29 30 31 . The ALD-grown Al:ZnO film is polycrystalline and the VO 2 thin film has an epitaxial relationship with the sapphire substrate of (010)[100]VO 2 (0001)[10-10]Al 2 O 3 as confirmed via symmetric [ Fig.…”

“…1(d) ]. Further details on these ALD pulsing sequences and Al:ZnO thin films are discussed elsewhere 30 31 .…”

Microstructural and optical properties of high-quality ZnO epitaxially grown on a LiGaO2 substrate

“…2,3 These unique properties make ZnO a potential material for applications in electronics, optoelectronics, acoustics, and sensing. [1][2][3] Various growth techniques have been used to fabricate ZnO thin lms, such as molecular beam epitaxy (MBE), 4,5 metal-organic chemical vapor deposition (MOCVD), 6,7 chemical vapor deposition (CVD), 8,9 pulsed laser deposition (PLD), 10,11 atomic layer deposition (ALD), 12,13 sputtering, 14,15 and sol-gel. 16 Among them, CVD gains particularly concerns because it is a simple and economic technique that has been widely used in the semiconductor industry to produce thin lms.…”

“…The crystal quality of asgrown ZnO thin lms is superior to previously reported ZnO lms grown on (001) LiGaO 2 substrate [25][26][27] and comparable to that of ZnO thin lms grown by MBE, MOCVD, PLD and ALD. [4][5][6][7][10][11][12][13] The underlying growth mechanism towards the high-quality ZnO lms is also discussed in detail.…”