化学浴法合成的CdS/Cd/Si纳米异质结：结构、合成与光学特性研究

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本文主要探讨了CdS/Cd/Si多界面纳米异质结（CdS:Cd/Si multi-interface nanoheterojunction）的合成、结构及其光学性质，由Yue Li Song等人在Pingdingshan University和Zhengzhou University的研究团队合作完成。这项研究发表于2015年，通过化学浴沉积法在硅纳米柱阵列（Silicon nanoporous pillar array, Si-NPA）上成功生长了CdS量子点（nc-CdS），从而构建出p型硅（n-type nc-CdS）之间的多界面异质结。首先，作者们采用了精细的实验方法，将CdS量子点精确地沉积在Si-NPA上，这一步骤对于形成稳定的异质结至关重要。Si-NPA的独特性质，如高比表面积和丰富的孔隙结构，使得Cd2+离子能够有效地在Si-NPA表面与溶液接触，部分被还原，从而形成稳定的Cd-Si界面。这种界面特性对异质结的性能有着显著影响。在结构方面，论文深入研究了这种异质结的微观形貌和界面特性。通过电子显微镜技术，研究人员得以观察到CdS量子点与Si基底的接口处的精细结构，这有助于理解光电子过程在这些界面处的行为。同时，多界面的存在可能导致不同的能级匹配，从而影响载流子传输和能量传递效率。光学性质是研究的核心部分，作者们利用了Tauc's关系来分析光吸收谱，这是评估半导体材料光学性质的重要工具。通过测量和解析光吸收数据，他们揭示了CdS:Cd/Si-NPA的带隙宽度和可能的缺陷态，这对于优化器件的设计和性能预测具有重要意义。此外，论文还讨论了光致发光（Photoluminescence）现象，探讨了异质结在光激发下的发光特性，包括可能的发射峰位置和强度，以及这些性质如何受到结构参数的影响。这项研究不仅展示了CdS:Cd/Si多界面纳米异质结的合成方法，还提供了对其物理特性和潜在应用的深入了解。由于其独特的结构和光学性能，这种异质结有潜力用于光电子设备，如太阳能电池、光探测器或光催化器等领域。未来的研究可能会集中在进一步优化异质结的性能，以提升这些应用的效能。

Synthesis, structures and optical properties of CdS:Cd/Si multi-interface

nanoheterojunction

Yue Li Song

, He Ying Bian

, Yong Li

a,b,

⇑

, Peng Fei Ji

, Shu Qing Yuan

, Feng Qun Zhou

, Xin Jian Li

Department of Physics and Solar Energy Research Center, Pingdingshan University, Pingdingshan 467000, PR China

Department of Physics and Laboratory of Materials Physics, Zhengzhou University, Zhengzhou 450052, PR China

article info

Article history:

Received 17 December 2014

Received in revised form 25 February 2015

Accepted 26 February 2015

Available online 4 March 2015

Keywords:

Silicon nanoporous pillar array (Si-NPA)

CdS:Cd/Si multi-interface

nanoheterojunction (CdS:Cd/Si-NPA)

Tauc’s relation

Photoluminescence

abstract

CdS/Si multi-interface nanoheterojunction is synthesized through depositing nanocrystals CdS (nc-CdS)

on the silicon nanoporous pillar array (Si-NPA) using a chemical bath deposition method. p-type

nanocrystals Si in Si-NPA and n-type nc-CdS construct the multi-interface nanoheterojunction. Due to

the reducibility of Si-NPA, a portion of Cd

in the interface of Si-NPA and solution are deoxidized and

nanocrystals Cd are simultaneously incorporated into the interface of Si–CdS, namely, CdS:Cd/Si-NPA.

Through decomposing the resolution XPS spectrum of Cd 3d, the ratio of Cd

and Cd

is about 0.7:1.

Three primary color emissions from CdS:Cd/Si-NPA are observed at the room temperature. Optical band

gap obtained by the Tauc’s relation and origins of emission bands are studied.

1. Introduction

Heterojunction (or Schottky junction) is the base of electronic

and optoelectronic devices, the investigation of which is carried

out to explore and control the transportation of electrons and

holes. For example, Huang et al. have studied the transportation

of carriers by introduction an intermediate layer into the interface

of heterojunction and controlled the electron blocking and holes

transportation [1,2]. Shao et al. have controlled the carriers trans-

portation through the polarity of the applied voltage [3]. CdS, a

direct wide band gap of 2.42 eV, is an excellent material in the

optoelectronic applications, such as solar cells, ﬁeld emission, pho-

todetectors and lasers [4–6]. As is known, the crystal Si has been a

dominant electronic material, and the nanoheterojunction based

on Si might be of key importance in the future optoelectronic

nanodevices. Silicon nanoporous pillar array (Si-NPA) is a

Si-based hierarchical structure characterized by a regular array of

micro-sized, quasi-identical and highly porous Si pillars con-

structed by silicon oxide encapsulated nanocrystal Si [7]. Based

on Si-NPA, CdS/Si nanoheterostructure have been fabricated, more-

over, the rectiﬁcation effect and obvious photovoltaic properties

have been observed in this structure [8,9], which illustrate that

CdS/Si nanoheterostructure might be a novel heterostructure

photovoltaic devices. The higher open circuit voltage has been

obtain in the photovoltaic device based on CdS/Si nanoheterostruc-

ture, however, the short circuit current and energy conversion efﬁ-

ciency are relatively low [9]. Through the analysis, the reason for

the lower short circuit current and energy conversion efﬁciency

is the higher series resistance. The adopted initial silicon wafers

are heavily boron-doped ones, the series resistance should mainly

originate from CdS thin ﬁlms [10]. The introduction of foreign atom

is a usually method to reduce the resistance of nanostructure

semiconductor.

In this article, a CdS/Si multi-interface nanoheterojunction is

fabricated by depositing CdS nanocrystal (nc-CdS) on Si-NPA using

the chemical bath deposition (CBD) method. Utilizing the

reducibility of Si-NPA, Cd

are deoxidized and nanocrystal Cd

(nc-Cd) are simultaneously incorporated into the interface of Si–

CdS, namely, CdS:Cd/Si-NPA. The structures and optical properties

of CdS:Cd/Si-NPA are studied in detail.

2. Experiments

The Si-NPA samples were prepared by hydrothermally etching p-type, (1 11)-

oriented single crystal silicon (sc-Si) wafers in the aqueous solution of hydroﬂuoric

acid containing ferric nitrate. The details about the preparing conditions and pro-

cesses have been reported previously [11]. The CdS thin ﬁlms were grown on Si-

NPA by a CBD method. Firstly, 0.685 g cadmium chloride (CdCl



O) was dis-

solved in the mixture solution of 15 ml 25–28% ammonia (NH

 H

O) and 65 ml

de-ionized water. Then the solution was poured into a bath and stirred with a mag-

netic agitation. The bath was kept at 80 °C for 60 min. Next, 5 ml 0.1 mol/l ammo-

nium chloride (NH

Cl) and 5 ml 2.0 mol/l thiourea (CH

S) were slowly added into

http://dx.doi.org/10.1016/j.jallcom.2015.02.199

⇑

Corresponding author at: Department of Physics and Solar Energy Research

Center, Pingdingshan University, Pingdingshan 467000, PR China.

E-mail address: liyong@pdsu.edu.cn (Y. Li).

Journal of Alloys and Compounds 637 (2015) 133–136

Contents lists available at ScienceDirect

Journal of Alloys and Compounds

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

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