ZnO1-xSx合金膜研究：结构、光学性质与S含量的关系

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"本文详细探讨了通过脉冲激光沉积法制备的单相ZnO1-xSx合金薄膜的结构和光学特性，重点关注带隙、晶格参数与硫含量的关系。研究发现，随着硫含量Xs从0增加到0.18，薄膜的晶格常数c和a逐渐增大，同时光学带隙减小。这些发现对于设计理想的ZnOS / MgZnO异质结构以及开发高性能的光电器件具有重要意义。" 在本文中，科研人员采用脉冲激光沉积技术在外延生长了高质量的ZnO1-xSx薄膜，其硫含量范围从0到0.18。ZnO1-xSx薄膜的结构分析表明，所有薄膜均保持了单一的纤锌矿结构，这一结果是通过X射线衍射(XRD)得出的。随着硫含量的增加，晶格常数c和a呈现出单调的扩张趋势，这意味着薄膜的晶格参数受到硫掺杂的影响，导致晶格的膨胀。这样的变化可能源于硫原子与锌和氧原子之间的化学键合性质差异。光学性质方面，研究发现ZnO1-xSx薄膜的光学带隙从3.27 eV下降到2.92 eV，这反映了带隙工程的潜力。带隙的变化通常与材料的电子结构有关，硫掺杂可能导致能带结构的调整，进而影响带隙宽度。此外，还观察到了一个弯曲参数为2.91 eV的现象，这可能与能带的非线性行为或者材料的复杂能级结构有关。这些结构和光学性质的改变对于设计新型光电器件至关重要。特别是，基于这些数据，可以预见到具有理想面内晶格匹配和最大势垒高度的ZnOS / MgZnO异质结构的可能性。这种异质结构能够促进载流子传输，提高器件效率，并且可能应用于太阳能电池、发光二极管(LED)或光电探测器等光电器件中。这项研究揭示了ZnO1-xSx合金薄膜中硫掺杂如何影响其结构和光学特性，为未来开发高性能、优化的光电子应用提供了理论基础和实验依据。通过精细调控硫含量，可以实现对薄膜性能的定制，以满足特定应用的需求。这些深入的理解和发现将推动脉冲激光沉积技术在薄膜材料制备领域的进一步发展。

Structural and optical properties of single-phase ZnO

1x

alloy ﬁlms

epitaxially grown by pulsed laser deposition

Yunbin He

⇑

, Lei Zhang

, Liangheng Wang

, Mingkai Li

, Xunzhong Shang

, Xiong Liu

, Yinmei Lu

a,b

Bruno K. Meyer

Key Laboratory of Green Preparation and Application for Functional Materials, Ministry of Education of China, Faculty of Materials Science & Engineering, Hubei University,

Wuhan 430062, China

I. Physikalisches Institut, Justus-Liebig-Universität Gießen, Heinrich-Buff-Ring 16, 35392 Gießen, Germany

article info

Article history:

Received 1 October 2013

Accepted 25 October 2013

Available online 5 November 2013

Keywords:

ZnOS alloy ﬁlms

Pulsed laser deposition

Epitaxial growth

Lattice parameters

Band gap

abstract

We report on a detailed investigation of the structural and optical properties of single crystalline ZnO

1x

thin ﬁlms, placing emphasis on the elucidation of the correlation of the band gap and lattice parameters,

particularly the lattice constant a, with the S content in the alloy ﬁlms. High-quality ZnO

1x

thin ﬁlms

with different S concentrations Xs(06 Xs 6 0.18) were grown epitaxially on c-plane sapphire substrates

by pulsed laser deposition using a ZnS ceramic target with varying O

partial pressures. X-ray diffraction

studies revealed that all grown ZnO

1x

thin ﬁlms have a single-phase wurtzite structure. With increas-

ing Xs value from 0 to 0.18, both lattice constants c and a expand monotonically from 5.204 to 5.366 Å

and from 3.255 to 3.329 Å, respectively, while the optical band gap shrinks from 3.27 to 2.92 eV with

a bowing parameter of 2.91 eV. Based on these information, ZnOS/MgZnO heterostructures that have a

perfect in-plane lattice match and a maximum barrier height can be proposed, which might eventually

lead to new optoelectronic devices with superior performance.

1. Introduction

ZnO is a typical wide band gap semiconductor (E

3.3 eV at

room temperature) that holds great promise for applications in

optoelectronic devices operating in the blue to ultraviolet spectral

region. Among the other advantages, its large exciton binding en-

ergy (60 meV) and oscillator strength could lead to laser action

based on exciton recombination at or even above room tempera-

ture [1,2]. Since the exciton binding energy and oscillator strength

can be further boosted at least twice in quantum conﬁned struc-

tures, ZnO based devices shall take advantage of quantum-well

(QW) structures to optimize the device performance [3]. Following

extensive investigations on the band gap engineering of ZnO by

isovalent cationic substitution (e.g. MgZnO, BeZnO and CdZnO al-

loys), constructing and fabricating single and multiple ZnO-based

QWs from ZnO/ZnMgO [4], ZnO/ZnBeO [5], CdZnO/ZnO [6], and

CdZnO/MgZnO [7] on various substrates have already been demon-

strated with different growth techniques. On the other hand, alloy-

ing of ZnO by isovalent anionic substitution [8], e.g. replacing

oxygen by sulfur, is far less explored, and documentation of ZnO-

based heterostructures involving ZnOS alloys is not available in

the literature up to date.

Yoo et al. [9] ﬁrst successfully doped S into ZnO with pulsed la-

ser deposition (PLD) by alternatively ablating a ZnO and a ZnS tar-

get. They found that the sulfur concentration in single-phase

wurtzite ZnOS ﬁlms deposited on c-plane sapphire at 700 °C was

limited to 0.13 and both the c-axis lattice constant and the band

gap showed a nonlinear correlation with the sulfur content in

the ﬁlms. Applying radio-frequency (RF) reactive sputtering and

using a ZnS ceramic target with Ar/O

as working/reactive gases,

Meyer et al. [10] synthesized single-phase wurtzite ZnO

1x

alloy

ﬁlms in the whole composition range (0 6 x 6 1) on both glass and

c-plane sapphire substrates at a relatively low substrate tempera-

ture of 340 °C, and found that the c-axis lattice constant changed

linearly while the band gap varied nonlinearly with the sulfur con-

tent x in the ZnOS alloys, and an optical bowing parameter of

3.0 eV was determined. With similar technique, Pan et al. [11]

deposited ZnO

1x

alloy ﬁlms on glass substrates at 300 °C with

post-annealing at 500–600 °C. They noticed a phase separation oc-

curred in the composition range of 0.23 < x < 0.77, and a non-linear

variation of the c-axis lattice constant and band gap with respect to

the S content in both the wurtzite O-rich (0 6 x 6 0.23) and

zincblende S-rich (0.77 6 x 6 1) ﬁlms. In a recent study, we used

the PLD technique, employing also a ZnS ceramic target with O

as the reactive gas to grow ZnOS alloy ﬁlms [12]. High-quality

epitaxial ﬁlms allowed us to determine the S solubility (up to

http://dx.doi.org/10.1016/j.jallcom.2013.10.201

⇑

Corresponding author. Tel./fax: +86 27 88661803.

E-mail addresses: ybhe@hubu.edu.cn, yunbin.he@physik.uni-giessen.de (Y. He).

Journal of Alloys and Compounds 587 (2014) 369–373

Contents lists available at ScienceDirect

Journal of Alloys and Compounds

journal homepage: www.elsevier.com/locate/jalcom

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