Superior pinning properties in nano-engineered YBa2Cu3O7-δ

Large electrical current transport in the absence of energy losses is the key factor in commercial applications of high temperature superconductors. This thesis demonstrates an easy and inexpensive bottom-up technique to produce self assembled nanorods, segmented nanorods as well as nanoparticles in YBa2Cu3O7-δ thin films grown by pulsed laser deposition. The structural and morphological characteristic of the pinning landscapes produced are investigated and correlated to their effects on the superconducting properties of the thin films. In particular two pinning landscapes are investigated: Ba2YNbO6 nanorods are grown in YBa2Cu3O7-δ thin films using a Ba2YNbO6 doped YBa2Cu3O7-δ pulsed laser deposition targets and Ba2(Y/Gd)(Nb/Ta)O6 segmented nanorods together with (Y/Gd)2O3 nanoparticles are grown in (Y/Gd)Ba2Cu3O7-δ thin films using a Ba2YNbO6 + Gd3TaO7 doped YBa2Cu3O7-δ pulsed laser deposition targets. The Ba2YNbO6 + YBa2Cu3O7-δ is deeply characterised and the effects of the deposition parameters are analysed. Ba2YNbO6 is demonstrated to be an interesting novel pinning addition capable to increase the critical current and to reduce the YBa2Cu3O7-δ critical currents angular dependencies anisotropy. The Ba2YNbO6 + Gd3TaO7 + YBa2Cu3O7-δ is found to produce a new complex pinning landscape extremely effective. At high fields the synergetic combination of the different defects typology is shown to generate an interesting new feature in the critical current angular dependencies. Chapter 1 is an introduction to superconductivity, the fundamentals of the field are briefly presented. In chapter 2 the discussion in focused on pinning in high temperature superconductors. Cuprates and in particular YBa2Cu3O7-δ are presented. The pinning phenomenon and the practical pinning engineering in thin films is also discussed in this chapter. Chapter 3 describes the thin films preparation methods and the characterisation techniques used in the research work. Chapter 4 and 5 are focused on the Ba2YNbO6 doped YBa2Cu3O7-δ thin films. Chapter 4 is an introduction to Ba2YNbO6 doped YBa2Cu3O7-δ, the preliminary results obtained on Ba2YNbO6 doped YBa2Cu3O7-δ thin films are shown in this chapter. The crystalline structure, the morphology and the superconducting properties of thin films deposited adopting different deposition parameters are analysed and discussed in chapter 5. In chapter 6 the new complex pinning landscape of Ba2(Y/Gd)(Nb/Ta)O6 and (Y/Gd)2O3 in (Y/Gd)Ba2Cu3O7-δ is presented. Concluding remarks on the research described in the work ends the thesis in a brief final chapter 7.The work described in this dissertetion was supported by NESPA, Nano-Engineered Superconductors for Power Application, a framework of the Marie Curie Research Training Network, funded within the EUs 6th framework program

Chemical and Geometric Transformations of MoS2/WS2 Heterostructures by Plasma Treatment

abstract: Two-dimensional (2D) transition metal dichalcogenides (TMDCs) like molybdenum disulfide (MoS2) and tungsten disulfide (WS2) are effective components in optoelectronic devices due to their tunable and attractive electric, optical and chemical properties. Combining different 2D TMDCs into either vertical or lateral heterostructures has been pursued to achieve new optical and electronic properties. Chemical treatments have also been pursued to effectively tune the properties of 2D TMDCs. Among many chemical routes that have been studied, plasma treatment is notable for being rapid and versatile. In Wang’s group earlier work, plasma treatment of MoS2 and WS2 resulted in the formation of MoO3 and WO3 nanosheets and nanoscrolls. However, plasma treatment of 2D TMDC heterostructures have not been widely studied. In this dissertation, MoS2/WS2 vertical and lateral heterostructures were grown and treated with air plasma. The result showed that the vertical heterostructure and lateral heterostructures behaved differently. For the vertical heterostructures, the top WS2 layer acts as a shield for the underlying MoS2 monolayer from oxidizing and forming transition metal oxide nanoscrolls, as shown by Raman spectroscopy and atomic force microscopy (AFM). On the contrary, for the lateral heterostructures, the WS2 that was grown surrounding the MoS2 triangular core served as a tight frame to stop the propagation of the oxidized MoS2, resulting a gradient of crack distribution. These findings provide insight into how plasma treatment can affect the formation of oxide in heterostructure, which can have further application in nanoelectronic devices and electrocatalysts.Dissertation/ThesisMasters Thesis Materials Science and Engineering 201

Study of Surface Morphology and Microstructure of Electrodeposited Polycrystalline Cu Films

The applications of polycrystalline films range from interconnects in the electronics and semiconductor industry to solar cells and as corrosion protection. Despite their significance, factors that determine their microstructure and morphology remain largely unsolved. The surface and microstructure of electrodeposited polycrystalline Cu films were investigated. This involves looking at the later growth stages of Cu films using different surface and bulk characterization techniques. The surface evolution of an electrodeposited Cu film was imaged in real-time using a Highspeed Atomic Force Microscope (HS-AFM). This provides details about how the film structure coarsens with time. The high-resolution video showed accelerated local grain growth and grain overgrowth at different locations of the film. A combination of both of these mechanisms could drive structural coarsening. The microstructure could play a role in inducing faster growth in certain grains. How the local and large-scale roughness varies with film thickness is studied by scaling analysis. As a complement to scaling analysis, variation in the local slope with thickness is calculated using slope analysis. Rapid growth was observed in the regions where the HS-AFM tip was scanning. The removal of oxygen adlayer from the surface by the tip could promote faster growth in these regions. Pulsed electrodeposition produced Cu films with hexagonal structures. They are known to be twinned which is a desirable feature in applications that require superior mechanical and electrical properties. The effect of electrode potential on grain size was studied. Using a watershed segmentation algorithm, the grain area was calculated from the AFM images. The grain area showed an increasing trend with increasing overpotential. Slope analysis on the ’hexagons’ and the complete films electrodeposited at higher potential revealed higher slopes and distinct slope distribution. Cross-sectional Focused Ion Beam (FIB) milling confirmed that horizontal twins are present in the pulse-deposited Cu films. The hexagonal pyramids with twins could be produced by one of the two mechanisms, stress relaxation during the ’OFF’ period of pulsing or driven by screw dislocation. We attribute the origin of the hexagons to spiralling screw dislocations. A template matching algorithm was developed to try and correlate the surface and microstructural data of a Cu film grown on a microelectrode. It involved matching the AFM and Electron Back Scatter Diffraction (EBSD) data on the later FIB milled sample, thus relating surface topography to crystallographic orientation. The crystallographic orientation of the edge of the microelectrode and its centre showed different orientations, switching from (111) to (110). Twinning was investigated at the edge and the centre of the microelectrode revealing the presence of stacking fault twins in both of these regions

Lead Free CH3NH3SNI3 Perovskite Thin-Film with P-type Semiconducting Nature and Metal-like Conductivity

CH3NH3SnI3 and CH3NH3PbI3 have become very promising light absorbing materials for photovoltaic devices over the last several years. CH3NH3PbI3 based perovskite solar cells have reached a solar-to-electricity conversion efficiency of ~ 22%. Nevertheless, CH3NH3PbI3 perovskite solar cells contain lead, which has serious consequences for the environment and human health. In this work, the lead was replaced with less toxic tin. Lead free CH3NH3SnI3 perovskite thin film was prepared by two low temperature solution processing methods and characterized using various tools such as Xray Diffraction (XRD) and absorption spectroscopy (UV-VIS). The distinctive p-type semiconducting nature and metal like conductivity of CH3NH3SnI3 were confirmed by the measurements of electrical and optical properties. Crystal structures and uniform film formation of CH3NH3SnI3 layer were analyzed by XRD and scanning electron microscopy (SEM). The CH3NH3SnI3 film morphology, uniformity, light absorption and electrical properties strongly depend on the preparation methods and precursor solutions. The CH3NH3SnI3 perovskites fabricated using dimethylformamide (DMF) exhibited higher crystallinity and stronger light harvesting capability than those fabricated using a blend solvent of dimethyl sulfoxide (DMSO) and gamma-butyrolactone (GBL). The local nanoscale photocurrent mapping confirmed that CH3NH3SnI3 can be used as an active layer and has a potential to fabricate lead free photovoltaic devices. The CH3NH3SnI3 film also showed a strong absorption in visible and near infrared spectrum with an absorption onset of 1.3 eV

변형된 이종구조 산화물 나노 결정의 성장, 원자 구조 및 촉매 특성에 관한 연구

학위논문 (박사) -- 서울대학교 대학원 : 공과대학 화학생물공학부(에너지환경 화학융합기술전공), 2020. 8. 현택환.Strain engineering of the inorganic nanocrystal is a promising approach necessary to address emerging global energy, resource, and environmental issues. When different materials are combined to produce heterostructured nanocrystal, the epitaxially-strained lattices can be formed at the heterointerface. In particular, the strain effect at the nanoscale can alter the surface lattice spacing and tune the electronic structure of the surface atoms, thus modifying the catalytic activity. The strain can be tuned by a lattice mismatch between the substrate and the overgrowth phase with a different crystal structure or crystallographic orientation. The strain engineering has been developed in heterostructured nanocrystals with different material combinations, including metals, semiconductors, and oxides. However, studies on the strained structure in oxide nanocrystals are limited because the synthesis of such structures has not been well established. In this thesis, I have designed and synthesized a model system that could investigate the strain effect on the regulation of the surface electronic structure for the design of better catalysts. The strained heterostructured oxide nanocrystals were produced using seed-mediated growth. The unique structure of these nanocrystals has been successfully studied with electron microscopy. The first part of this thesis is an overview of epitaxial growth in thin-film technology and its analogy to three-dimensional (3D) polyhedral epitaxial growth. Chapter 2 describes the design principles for producing highly ordered multigrain nanostructures. Identification of the principles was achieved by synthesizing the nanocrystals with misfit-strain-induced uniform grain boundary defects, imaging the deformed structure at the nanometer scale using a scanning transmission electron microscopy (STEM), and measuring the strain field. The seed-mediated approach was used to grow Mn3O4 grains on a cubic Co3O4¬ nanocrystal core. The facets of the cube nanocrystal substrates can guide the growth direction of the shell, creating a gap between the lattices of the adjacent Mn3O4 grains. Unlike the previous studies on the heteroepitaxial strains, the grain boundary (GB) defects in this new multigrain nanocrystal were induced by the geometric misfit strain between the adjacent Mn3O4 grains. Since the defects occur along the edges of the core, a uniform core shape is a prerequisite for achieving uniform GB defects. The strain tensor near the GB lattices reveals that the Mn3O4 shell accommodates a large epitaxial strain per GB without dislocation. Chapter 3 presents the epitaxially strained CeO2/Mn3O4 nanocrystals for antioxidant applications. The Mn3O4 lattices are highly strained due to the large lattice mismatch between CeO2 and Mn3O4. The heterostructured nanocrystals with different compositions were prepared to study the strain effect by comparing the surface oxygen vacancy and the characteristics of surface reducibility. Due to the enhanced ability to scavenge the reactive oxygen species (ROS), the nanocrystal with strained Mn3O4 layer can protect the hematopoietic intestinal stem cells from irradiation.무기 나노 결정의 변형 엔지니어링은 에너지, 자원 및 환경과 같은 전 지구적인 문제를 해결하는 데 필요한 유망한 접근법이다. 서로 다른 재료를 조합하여 이종 구조화된 나노 결정을 생성할 때, 에피택셜 변형된 격자는 이종 계면에 형성될 수 있다. 특히, 나노 규모에서의 변형 효과는 표면의 격자 간격을 변경하고 표면 원자의 전자 구조를 조정하여, 촉매 활성을 변형시킬 수 있다. 변형은 상이한 결정 구조나 결정학적 배향의 기판과 증착상 사이의 격자 부정합에 의해 조정된다. 변형 엔지니어링은 금속, 반도체 및 산화물을 포함한 다양한 재료 조합된 이종구조 나노 결정에서 개발되어 왔다. 그러나 산화물 나노 결정에서의 변형 구조에 대한 연구는 이러한 구조의 합성법이 잘 확립되지 않았기 때문에 제한적이다. 이 논문에서, 더 나은 촉매의 설계를 위하여 표면의 전자 구조 조절에 대한 변형 효과를 연구할 수 있는 모델 시스템을 설계하고 합성했다. 변형된 이종구조 산화물 나노 결정은 종자 매개 성장을 사용하여 제조되었다. 이러한 나노 결정의 독특한 구조는 전자 현미경으로 성공적으로 연구되었다. 이 논문의 1장은 2차원 박막 기술의 에피택셜 성장과 3 차원 다면체와의 유사성에 대한 개요이다. 2 장은 고도로 정돈된 멀티 그레인 나노 구조를 생성하기 위한 설계 원리를 설명한다. 원리 발견은 부정합 변형이 유발된 균일한 경계 결함으로 나노 결정을 합성하고, 주사 투과 전자 현미경을 사용하여 나노 미터 스케일에서 변형된 구조를 이미징하고, 변형 장을 측정함으로써 달성되었다. 시드 매개 접근법을 사용하여 입방형 Co3O4 결정 코어에서 Mn3O4 입자를 성장시킬 수 있다. 기판인 입방체 나노 결정의 면은 쉘의 성장 방향을 안내 할 수 있고, 인접한 Mn3O4 입자의 격자 사이에 틈을 생성한다. 이종 에피택셜 변형에 대한 이전의 연구와는 달리, 이 새로운 다결정 나노 결정에서의 입자 경계 결함은 인접한 Mn3O4 입자 사이의 기하학적 부정합 변형에 의해 유발되었다. 결함은 코어의 가장자리를 따라 발생하기 떄문에 균일한 경계 결함을 달성하기 위해서는 균일한 형상의 코어가 전제 조건이다. 경계 결함 격자 근처의 변형 텐서는 Mn3O4 쉘이 전위 없이 경계 결함 당 큰 에피택셜 변형을 수용한다는 것을 보여준다. 3 장에서는 항산화제 적용을 위한 에피택셜 변형된 CeO2/Mn3O4 나노 결정을 제시한다. Mn3O4 격자는 CeO2와 Mn3O4 사이의 큰 격자 부정합으로 인해 상당히 변형된다. 상이한 조성을 갖는 이종 구조화된 나노 결정을 제조하여 표면 산소 공극 및 표면 환원 특성에 대한 변형 효과를 비교, 연구하였다. 향상된 활성산소 제거 능력을 나타내는 변형된 Mn3O4 층을 갖는 나노 결정을 이용하여 조혈장 줄기 세포를 방사선 조사로부터 보호할 수 있었다.Chapter 1 Introduction: Synthetic Methods for Epitaxially Strained Heterostructured Nanocrystals .........................1 1.1 Thin-film epitaxy in nanomaterials .......................................................1 1.1.1 Thin-film deposition techniques .................................................1 1.1.2 Growth modes ............................................................................4 1.2 Strain engineering ...............................................................................13 1.2.1 Synthesis of heterostructured nanocrystals ...............................13 1.2.2 Strain in heterostructured nanocrystals .....................................19 1.2.3 Characterization of strained nanocrystals for catalysis .............28 1.3 Dissertation Overview ........................................................................35 1.4 References ...........................................................................................38 Chapter 2 Design and Synthesis of Multigrain Nanocrystals via Geometric Misfit Strain ..................................................44 2.1 Introduction .........................................................................................44 2.2 Experimental Section ..........................................................................46 2.3 Result and Discussion .........................................................................52 2.4 Conclusion ........................................................................................130 2.5 References .........................................................................................131 Chapter 3 Epitaxially Strained CeO2/Mn3O4 Nanocrystals as an Enhanced Antioxidant for Radioprotection ...........137 3.1 Introduction .......................................................................................137 3.2 Experimental Section ........................................................................139 3.3 Result and Discussion .......................................................................145 3.4 Conclusion ........................................................................................176 3.5 References .........................................................................................177 국문 초록 (Abstract in Korean) ..........................................182Docto

Caracterización estructural y funcional de películas delgadas nanoporosas mediante microscopías electrónicas de transmisiónbarrido y espectroscopías ópticas

Nano-structuration of materials at the mesoscale to give rise to porosity-controlled coatings represents an important breakthrough in the area of Materials Science and Engineering, offering new and enhanced functionalities of interest in fields such as optics, optronics and optoelectronics. In order to optimize their performances, in-depth analyses are required: local information about the morphology, composition and atomic structure, the compactness distribution, but also layer homogeneity, interface and interpenetration between stacked layers or oxidation are extremely important factors that can ruin their way of operation. In this particular context, the objective of the present PhD Thesis is to make significant contributions to the study and development of multifunctional porous nanostructured systems, from their design and elaboration, to the maximum knowledge of their structure and properties, through advanced (S)TEM methods, including 3D reconstructions, elemental analyses at the nanoscale and atomic-scale imaging, combined with optical spectroscopy techniques. In the first instance, given the great potential of the slanted nanostructures generated by means of oblique angle depositions, in which the refractive index gradient can be tuned by the columns tilt and density imposed via the growth angles and parameters, OAD broadband antireflective coatings based on Si, Ge or SiO2 OAD films have been designed, manufactured, and extensively characterized with the aim of maximizing the performance of the optical elements in the vis-IR wavelength range. This same approach has also been implemented to enhance the antireflective capabilities of transparent conductive ITO thin films in the near-IR window without compromising too much their electrical response. On the other hand, the advanced structural and functional characterization of porosity-controlled GaN NW arrays grown by plasma-assisted MBE through (S)TEM methods and vis-IR SE elliposmetry, has helped not only to improve growth processes but also to optimize their resulting optical and electrical properties. Finally, the knowledge and methodologies acquired during the study and optimization of the previous porous systems have been transferred to the development of a two-step procedure, based on the deposition and the subsequent fast oxidation of vanadium-based OAD films in open air atmosphere, for the synthesis of thermochromic VO2 coatings of tunable metal-to-insulator response and controlled grain sizes and crystallinities

Microstructure Analysis and Surface Planarization of Excimer-laser Annealed Si Thin Films

The excimer-laser annealed (ELA) polycrystalline silicon (p-Si or polysilicon) thin film, which influences more than 100-billion-dollar display market, is the backplane material of the modern advanced LCD and OLED products. The microstructure (i.e. ELA microstructure) and surface morphology of an ELA p-Si thin film are the two main factors determining the material properties, and they significantly affect the performance of the subsequently fabricated thin film transistors (TFTs). The microstructure is the result of a rather complex crystallization process during the ELA which is characterized as far-from-equilibrium, multiple-pulse-per-area and processing-parameter dependent. Studies of the ELA microstructure and the surface morphology closely related to the device performance as well as the microstructure evolution during the ELA process are long-termly demanded by both the scientific research and the industrial applications, but unfortunately have not been thoroughly performed in the past. The main device-performance-related characteristics of the ELA microstructure are generally considered to be the grain size and the presence of the dense grain boundaries. In the work of this thesis, an image-processing-based program (referred to as the GB extraction program) is developed to extract the grain boundary map (GB map) out of the transmission electron microscope (TEM) images of the ELA microstructure. The grain sizes are straightforwardly calculated from the GB map and statistically analyzed. More importantly, based on the GB maps, we propose and perform a rigorous scheme that we call the local-microstructure analysis (LMA) to quantitatively and systematically analyze the spatial distribution of the grain boundaries. The “local area” is mainly defined by the geometry and the location of a TFT. The successful extraction of the GB map and the subsequent LMA are permitted by our unique TEM skills to produce high-resolution TEM micrographs containing statistically significant number of grains for sensible quantitative analysis. The LMA unprecedentedly enables quantitative and rigorous analysis of spatial characteristics of the microstructure, especially the device geometry- and location-related characteristics. Additionally, we present and highlight the benefits of the LMA approach over the traditional statistical grain-size analysis of the ELA microstructure. From the grain-size analysis, we find that grain size across a statistically significant number of grains generally follows the same distribution as in the stochastic grain growth scenario at the beginning of the ELA process when the laser pulse (i.e. shot) number is small. As the shot number increases, the overall grain size monotonically increases while the distribution profile becomes broader. When the scan number reaches the ELA threshold (several tens of laser shots), the distribution profile substantially deviates from the stochastic profile and shows two sharp peaks in grain size around 300nm and 450nm, which is consistent with the previously proposed theory of energy coupling and nonuniform energy deposition during ELA. From the LMA, local nonuniformity of grain boundary density (GB density) at the device length scales and regions of high grain boundary periodicity are identified. More importantly, we find that the local nonuniformity is much more pronounced when p-Si film exhibits some level of spatial ordering, but less pronounced for a random grain arrangement. It is worth noting that the devices of different sizes and orientation have different sensitivity to the local nonuniformity of the ELA-generated p-Si thin film. In addition, based on the analysis results, the connection between the microstructure evolution and the partial melting and resolidification process of the Si film is discussed. Aside from the microstructure, the surface morphology of the ELA films, featuring pronounced surface protrusions, is characterized via an atomic force microscope (AFM). Attempts to planarize those surface protrusions detrimental to the subsequent device performance are conducted. In the attempts, the as-is (oxide-capped) ELA films and the BHF-treated ELA films are subjected to single shots of excimer irradiation. When the results are compared, an anisotropic melting phenomenon of the p-Si grains is identified, which appears to be strongly affected by the presence of the surface oxide capping layer. Conceptual models are developed and numerical simulations are employed to explain the observation of the anisotropic melting phenomenon and the effect of the surface oxide layer. Eventually, 41.8% reduction of root mean square (RMS) surface roughness is achieved for BHF-treated ELA films. The results gained in the systematic analysis of the ELA microstructure and the attempt of surface planarization further our understanding about (1) the device performance-related material microstructure of the ELA p-Si thin films, (2) the microstructure evolution occurring during multiple shots of the ELA process, and (3) the fundamental phase transformations in the far-from-equilibrium melt-mediated excimer-laser annealing processing of p-Si thin films. Such understanding could help engineers when designing the microelectronic devices and the ELA manufacturing process, as well as provide scientific researchers with insights on the melting and solidification of general polycrystalline materials, thus profoundly contributing to both the related scientific society and the technological community. The GB extraction program and the LMA scheme developed and demonstrated in the thesis, as another contribution to the related research filed, could also be generalized to the microstructural study of other polycrystalline materials where grain geometry and arrangement are of concern

Development and analyses of innovative thin films for photovoltaic applications

In solar cell current research, innovative solutions and materials are continuously requested for efficiency improvements. Si-based technology rules over 95% of the market, with silicon heterojunction (SHJ) solar cell reaching 26.7% record efficiency. Nonetheless, hydrogenated amorphous silicon (a-Si:H) layers employed in the structure still have challenges, resolvable with oxygen/nitrogen inclusion. In parallel, new technologies based on different materials still lack in the market due to stability issues or low efficiencies. However, a preliminary study of their properties creates a deeper knowledge exploitable in photovoltaic application. In this perspective, we investigated both innovative Si-based materials (nanocrystalline and amorphous silicon oxy-nitride and oxide thin films, nc-SiOxNy, a-SiOxNy and a-SiOx, respectively) and innovative materials (perovskite lanthanum-vanadium oxide LaVO3 thin films, indium gallium nitride InxGa1-xN and aluminium indium gallium nitride AlxInyGa1-x-yN layers) for solar cell concepts. Different deposition conditions have been employed to extract their influence on compositional, optical, and electrical properties. The study on nc-SiOxNy layers by conductive atomic force microscopy (c-AFM) and surface photovoltage (SPV) has allowed to clarify O, N, and B content, and annealing treatment role on microscopic transport properties. On a-SiOx and a-SiOxNy layers, by spectral ellipsometry, Fourier transform infrared spectroscopy, photoconductance decay and SPV, we can conclude that moderate insertions of O/N in a-Si:H lead to a decrease of optical parasitic absorption, preserving the passivation quality of the layers. The measurements by AFM and Kelvin probe force microscopy on LaVO3 have clearly shown that it is a poor charge-transport medium, thus not suitable for photovoltaic applications. The analysis on InGaN and AlGaInN by SPV measurements has shown how low In content, Si doping and no misfit dislocations in InGaN/GaN structure cause less recombination processes at the interface, whereas, the strain relaxation (tensile and compressive) with the formation of pinholes produces better interfaces in the AlGaInN/GaN samples

Influence of the substrate-induced strain and irradiation disorder on the Peierls transition in TTF-TCNQ microdomains

The influence of the combined effects of substrate-induced strain, finite size and electron irradiation-induced defects have been studied on individual micron-sized domains of the organic charge transfer compound tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) by temperature-dependent conductivity and current-voltage measurements. The individual domains have been isolated by focused ion beam etching and electrically contacted by focused ion and electron beam induced deposition of metallic contacts. The temperature-dependent conductivity follows a variable range hopping behavior which shows a crossover of the exponent as the Peierls transition is approached. The low temperature behavior is analyzed within the segmented rod model of Fogler, Teber and Shklowskii, as originally developed for a charge-ordered quasi one-dimensional electron crystal. The results are compared with data obtained on as-grown and electron irradiated epitaxial TTF-TCNQ thin films of the two-domain type