Structural and Physical Property Studies of Amorphous Zn–In–Sn–O Thin Films

Abstract

The structures in amorphous (a‐) Zn, Sn co‐doped In2O3 (ZITO) thin films grown by pulsed laser deposition on glass under varying oxygen pressure or with varying Sn:Zn ratios were determined using X‐ray absorption spectroscopy and anomalous X‐ray scattering. Typical structures around cations in a‐ZITO films are described and compared with crystalline (c‐) ZITO films. The results show that the Zn cations are fourfold coordinated with Zn–O bond lengths of 1.98 ± 0.02 Å, which is close to that in bulk ZnO. As a consequence, the second coordination shells around Zn contract. At longer distances away from Zn, the structure is commensurate with the averaged structure. The unit volume around In also contracts slightly compared to bulk In2O3, whereas the Sn–O bond length is similar to the one in bulk SnO2. These unique structural characteristics may account for the films' superior thermal stability over amorphous Sn‐doped In2O3, and suggest that Zn and Sn act as network‐forming cations. Like in c‐ZITO, coordination numbers (N) around Sn, In, and Zn follow the order NSn > NIn > NZn. Unlike in c‐ZITO, where electrical properties change significantly with a slight variation in the Sn:Zn ratio, this variation does not markedly alter the electrical properties, or the local structures, of a‐ZITO films. Dramatic changes in the electrical properties occur for films grown under various oxygen pressures, which point to oxygen “defects” as the source of charge carriers.

Relationship between electrical properties and crystallization of indium oxide thin films using ex-situ grazing-incidence wide-angle x-ray scattering

“…As mentioned in the Introduction, in-plane and crossplane measurements of electrical 23,24 and thermal 24 conductivities on other materials show that electronic transport and thermal conductivity are highly anisotropic. The in-plane vs cross-plane electrical conductivity of Ge/Si films can vary by a factor of five, while the in-plane vs cross-plane thermal conductivities can differ significantly, by a factor of 675 in graphene oxide.…”

“…17 EXAFS and molecular dynamics simulations related the local mobility maxima to structural factors. The amorphous and highly crystalline structures of zinc-indium-tin oxide (ZITO) have also been reported, 18,24,25 and a local maximum in l just prior to the observation of crystallization is also observed. 18 The interplay between the structure and properties revealed by amorphous and crystalline films warrants a closer look, with the promise of yielding insights that could be used to further improve and expand the applications of these films.…”

How does the multiple constituent affect the carrier generation and charge transport in multicomponent TCOs of In–Zn–Sn oxide

“…crystallizes in the C-type rare-earth (bixbyite) structure (space group Ia3, number 206). 52 First-principles calculations based on density functional theory implemented in the Vienna ab initio simulation package (VASP) 53,54 have been carried out. 1(a).…”

Structural and physical properties of transparent conducting, amorphous Zn-doped SnO2 films

“…Moreover, the electrical properties deteriorated significantly, which is believed to be due to the reduction from Sn 4þ to Sn 2þ , as suggested for a-ZITO films. 21 Fig . 8 compares the first derivatives of the Sn L 1 edge XANES measured on the a-ZTO90 films, deposited at 10 mTorr and 7.5 mTorr, and bulk SnO 2 .…”

“…X-ray absorption spectroscopy techniques 20 are well suited for the structural studies of disordered materials. Prior studies have used these techniques to probe the local structures of amorphous material systems such as Zn-In-Sn-O (ZITO), 21 In-Zn-O (IZO), 22 and In-Ga-Zn-O (IGZO), 23,24 i.e., the bond distances and coordination numbers, around specific cations. However, structure-property relationships have yet to be established.…”