Crystal Orientation-Ordered ZnS Nanowire Bundles

Abstract

Due to their potential applications, ranging from nanoscale electronic devices to tools for biomedical applications, onedimensional semiconductor nanostructures, such as nanowires and nanobelts, offer a high degree of interest for furthering the current state of nanotechnology research and development. Nanorods, 1 nanowires, 2 nanotubes, 3 and nanobelts 4 of various materials have been successfully synthesized, and they demonstrate novel luminescent, electronic, optical, and mechanical properties.ZnS is a direct wide band gap (3.91 eV) compound semiconductor that has a high index of refraction and a high transmittance in the visible range and is one of the most important materials in photonics research. 5 As a one-dimensional nanostructure, ZnS has been synthesized as nanowires, nanobelts, and nanocombs, but these nanostructures are randomly distributed on the surface of the substrate. 6,7 For applications in photonics, it is needed to create ZnS nanostructures that are highly aligned and ordered, but this type of structure has not been realized experimentally. In this paper, we report a novel approach for growing aligned and orientationordered ZnS nanowires. Our method relies on a buffer layer of CdSe grown on a Si(111) substrate, on which ZnS nanowires are grown. The growth process of the nanowire bundles is presented. The technique demonstrated could be an effective pathway for growing patterned, aligned, size-controlled, and orientation-ordered ZnS nanowires.The orientation-ordered ZnS nanowire bundles were synthesized through a two-step thermal evaporation process in a horizontal tube furnace. Commercially available CdSe powder (Alfa Aesar, 99.995% purity, metal basis) was placed in the center of a single-zone tube furnace (Thermolyne 79300). A vacuum was pulled into the tube for several hours to purge oxygen from the chamber. After evacuation to less than 2 × 10 -2 Torr, the temperature in the center of the tube was elevated to 750°C at a rate of 30°/min. A nitrogen (N 2 ) gas flow was introduced into the system at a rate of 50 sccm. The gas acted as a carrier for transporting the sublimated vapor to cooler regions within the tube furnace for deposition. The pressure was maintained at 300 mbar. The silicon substrates reached a temperature of about 575°C. After 1 h, the furnace was allowed to cool. Then, the source material of CdSe powder was replaced by commercially available ZnS powder (Alfa Aesar, 99.99% purity, metal basis). The temperature in the center of the tube was elevated to 1050°C. Again, a nitrogen gas flow was introduced at 50 sccm, and the pressure was maintained at 300 mbar. The silicon substrates reached a temperature of about 750°C. The system was held in this condition for a period of 60 min. Single-crystal silicon substrates were used for synthesizing the nanostructures. These substrates were placed downstream from the source material to collect the deposited nanostructures.The sample was analyzed on a scanning electron microscope (SEM). The deposited material has an extremely high yie...

Synthesis and Cathodoluminescence of Morphology-Tunable SiO2 Nanotubes and ZnS/SiO2 Core−Shell Structures Using CdSe Nanocrystals as the Seeds

“…54 Furthermore, CdSe and ZnS have similar structures, 55 and an effective epitaxial growth would be preferred to minimize the interface lattice mismatch. These behaviors are well known, and similar phenomena were observed by Wang et al 56 Because of the anisotropic nature of wurtzite ZnS phases, 1D ZnS nanowires are rapidly formed. Because of the relative good epitaxial lattice match between the wurtzite ZnS (010) plane and cubic CdSe (111) plane, the ZnS nanowires probably grow along the [01-10] direction, which is different from the conventional [0001] orientation.…”

ZnS Nanostructure Arrays: A Developing Material Star

“…[ 65 ] Besides the above example, heteroepitaxial growth of ZnS nanowire arrays on various substrates (such as CdSe, CdS, Zn 3 P 2 , Si and metal Zn foil) has been demonstrated successfully. [66][67][68][69][70] Figure 4 displays the SEM images of the as-grown ZnS nanowire arrays synthesized on the CdSe, CdS, Zn 3 P 2 and Si substrates by various methods, revealing all of the nanowires are orientationally aligned on the top of the corresponding substrates. These examples not only unveil that ZnS nanowire arrays not only can be obtained by a direct evaporationcondensation approach or a two-step thermal evaporation process, but also that the growth mechanism can be catalystfree VS or metal-catalyzed VLS growth processes.…”

Synthesis of Semiconducting Functional Materials in Solution: From II‐VI Semiconductor to Inorganic–Organic Hybrid Semiconductor Nanomaterials

“…Many methods have been developed to fabricate II-VI semiconductor nanostructures [8] such as wet-chemical methods, including solvothermal/hydrothermal method [9][10][11][12][13][14][15][16][17][18][19][20] and capping agent/surfactant assisted soft synthesis approach, [1,[21][22][23][24][25][26][27][28][29] sonochemical methods, [30][31][32] templating methods, [33][34][35][36] selfassembly oriented attachment growth, [37][38][39] and chemical vapor deposition (CVD) method. [40][41][42][43][44][45][46][47] On the other hand, hybrid structures consisted of semiconducting organic slabs and strongly luminescent II-VI semiconductor nanostructures offer favorable perspectives through highly saturated, tunable optical properties, in combination with an easy process-ability from solution and low cost of precursors, which is of importance for high-tech applications such as hybrid organic-inorganic light-emitting diodes and solar cells. [48][49]…”

“…[40][41][42][43][44][45][46][47] On the other hand, hybrid structures consisted of semiconducting organic slabs and strongly luminescent II-VI semiconductor nanostructures offer favorable perspectives through highly saturated, tunable optical properties, in combination with an easy process-ability from solution and low cost of precursors, which is of importance for high-tech applications such as hybrid organic-inorganic light-emitting diodes and solar cells. [48][49][50] In recent years, novel nanostructures of functional II-VI semiconductor chalcogenides, including nanobelts, nanowires, nanosaws, nanocombs and nanowindmills have been synthesized using thermal evaporation method by Wang's group [42,44,[51][52][53][54][55][56][57][58][59][60] and Lee's group. [61][62][63][64][65][66] In contrast to the traditional thermal evaporation routes or chemical vapor deposition (CVD) method, even hard template approaches, solution chemistry based so-called ''soft'' approaches can provide an alternative, convenient, lower temperature, and environmentally friendly pathway for fabrication of advanced inorganic materials with desirable shapes and sizes, [67] which do not rely on drastic conditions (i.e., high temperature, high pressure etc.…”