<?xml version="1.0" encoding="ISO-8859-1"?><article xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<front>
<journal-meta>
<journal-id>0035-001X</journal-id>
<journal-title><![CDATA[Revista mexicana de física]]></journal-title>
<abbrev-journal-title><![CDATA[Rev. mex. fis.]]></abbrev-journal-title>
<issn>0035-001X</issn>
<publisher>
<publisher-name><![CDATA[Sociedad Mexicana de Física]]></publisher-name>
</publisher>
</journal-meta>
<article-meta>
<article-id>S0035-001X2019000100005</article-id>
<title-group>
<article-title xml:lang="en"><![CDATA[Urbach&#8217;s tail in the absorption spectra of Cu2GeSe3 semiconducting compound]]></article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Rincón]]></surname>
<given-names><![CDATA[C.]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Marcano]]></surname>
<given-names><![CDATA[G.]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Wasim]]></surname>
<given-names><![CDATA[S. M.]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Marín]]></surname>
<given-names><![CDATA[G.]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Villareal]]></surname>
<given-names><![CDATA[M.]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Sánchez Pérez]]></surname>
<given-names><![CDATA[G.]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
</contrib-group>
<aff id="Af1">
<institution><![CDATA[,Universidad de Los Andes Facultad de Ciencias Centro de Estudios de Semiconductores]]></institution>
<addr-line><![CDATA[Merida ]]></addr-line>
<country>Venezuela</country>
</aff>
<aff id="Af2">
<institution><![CDATA[,Instituto Venezolano de Investigaciones Científicas Centro de Investigacion y Tecnología de Materiales Laboratorio de Estructura e Ingeniería de Materiales Nanoestructurados]]></institution>
<addr-line><![CDATA[Maracaibo ]]></addr-line>
<country>Venezuela</country>
</aff>
<pub-date pub-type="pub">
<day>00</day>
<month>02</month>
<year>2019</year>
</pub-date>
<pub-date pub-type="epub">
<day>00</day>
<month>02</month>
<year>2019</year>
</pub-date>
<volume>65</volume>
<numero>1</numero>
<fpage>5</fpage>
<lpage>9</lpage>
<copyright-statement/>
<copyright-year/>
<self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_arttext&amp;pid=S0035-001X2019000100005&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_abstract&amp;pid=S0035-001X2019000100005&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_pdf&amp;pid=S0035-001X2019000100005&amp;lng=en&amp;nrm=iso"></self-uri><abstract abstract-type="short" xml:lang="en"><p><![CDATA[Abstract In the present work we report on the analysis of the Urbach&#8217;s tail in pure and Mn-doped Cu2GeSe3 samples having small deviation from its ideal stoichiometry. It is found that the high values of the phonon energy h&#957;  p involved in the electrons/excitons-phonon interaction in the formation of this tail are due to structural disorder caused by deviation from ideal stoichiometry. Values of h&#957;  p for pure and doped samples were found to be 48, 60 and 81 meV, respectively, whereas the phonon energy for an entirely ordered Cu2GeSe3 sample was estimated to be about 25 meV.]]></p></abstract>
<kwd-group>
<kwd lng="en"><![CDATA[Optical absorption]]></kwd>
<kwd lng="en"><![CDATA[Urbach&#8217;s tail]]></kwd>
<kwd lng="en"><![CDATA[ternary compound]]></kwd>
<kwd lng="en"><![CDATA[structural defects]]></kwd>
<kwd lng="en"><![CDATA[71.20.Nr]]></kwd>
<kwd lng="en"><![CDATA[71.55.Jv]]></kwd>
<kwd lng="en"><![CDATA[78.30.Hv]]></kwd>
</kwd-group>
</article-meta>
</front><back>
<ref-list>
<ref id="B1">
<label>1</label><nlm-citation citation-type="">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Cho]]></surname>
<given-names><![CDATA[J. Y.]]></given-names>
</name>
</person-group>
<source><![CDATA[J. Alloy. Compd]]></source>
<year>2010</year>
<volume>18</volume>
<page-range>506</page-range></nlm-citation>
</ref>
<ref id="B2">
<label>2</label><nlm-citation citation-type="">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Skoug]]></surname>
<given-names><![CDATA[E. J.]]></given-names>
</name>
<name>
<surname><![CDATA[Cain]]></surname>
<given-names><![CDATA[J. D.]]></given-names>
</name>
<name>
<surname><![CDATA[Morelli]]></surname>
<given-names><![CDATA[D. T.]]></given-names>
</name>
</person-group>
<source><![CDATA[J. Alloy. Compd]]></source>
<year>2010</year>
<volume>18</volume>
<page-range>506</page-range></nlm-citation>
</ref>
<ref id="B3">
<label>3</label><nlm-citation citation-type="">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Cho]]></surname>
<given-names><![CDATA[J. Y.]]></given-names>
</name>
</person-group>
<source><![CDATA[Phys. Rev. B]]></source>
<year>2011</year>
<volume>84</volume>
</nlm-citation>
</ref>
<ref id="B4">
<label>4</label><nlm-citation citation-type="">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Ibáñez]]></surname>
<given-names><![CDATA[M.]]></given-names>
</name>
</person-group>
<source><![CDATA[Chem. Mater.]]></source>
<year>2012</year>
<volume>24</volume>
</nlm-citation>
</ref>
<ref id="B5">
<label>5</label><nlm-citation citation-type="">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Chetty]]></surname>
<given-names><![CDATA[R.]]></given-names>
</name>
</person-group>
<source><![CDATA[Intermetallics]]></source>
<year>2014</year>
<volume>54</volume>
<page-range>1</page-range></nlm-citation>
</ref>
<ref id="B6">
<label>6</label><nlm-citation citation-type="">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Qiu]]></surname>
<given-names><![CDATA[P.]]></given-names>
</name>
<name>
<surname><![CDATA[X. Shi]]></surname>
<given-names><![CDATA[L.]]></given-names>
</name>
</person-group>
<source><![CDATA[Chen, Energy Storage Materials]]></source>
<year>2016</year>
<volume>3</volume>
<page-range>85</page-range></nlm-citation>
</ref>
<ref id="B7">
<label>7</label><nlm-citation citation-type="">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Coughlan]]></surname>
<given-names><![CDATA[C.]]></given-names>
</name>
</person-group>
<source><![CDATA[Chem. Rev.]]></source>
<year>2017</year>
<volume>117</volume>
</nlm-citation>
</ref>
<ref id="B8">
<label>8</label><nlm-citation citation-type="">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Lee]]></surname>
<given-names><![CDATA[J. J.]]></given-names>
</name>
<name>
<surname><![CDATA[Yang]]></surname>
<given-names><![CDATA[C. S.]]></given-names>
</name>
<name>
<surname><![CDATA[Park]]></surname>
<given-names><![CDATA[Y. S.]]></given-names>
</name>
<name>
<surname><![CDATA[Kim]]></surname>
<given-names><![CDATA[K. H.]]></given-names>
</name>
</person-group>
<source><![CDATA[J. Appl. Phys.]]></source>
<year>1999</year>
<volume>86</volume>
</nlm-citation>
</ref>
<ref id="B9">
<label>9</label><nlm-citation citation-type="">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Marcano]]></surname>
<given-names><![CDATA[G.]]></given-names>
</name>
<name>
<surname><![CDATA[Nieves]]></surname>
<given-names><![CDATA[L.]]></given-names>
</name>
</person-group>
<source><![CDATA[J. Appl. Phys.]]></source>
<year>2000</year>
<volume>87</volume>
</nlm-citation>
</ref>
<ref id="B10">
<label>10</label><nlm-citation citation-type="">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Marcano]]></surname>
<given-names><![CDATA[G.]]></given-names>
</name>
</person-group>
<source><![CDATA[J. Appl. Phys.]]></source>
<year>2000</year>
<volume>88</volume>
</nlm-citation>
</ref>
<ref id="B11">
<label>11</label><nlm-citation citation-type="">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Choi]]></surname>
<given-names><![CDATA[S. G.]]></given-names>
</name>
</person-group>
<source><![CDATA[Appl. Phys. Lett.]]></source>
<year>2015</year>
<volume>106</volume>
</nlm-citation>
</ref>
<ref id="B12">
<label>12</label><nlm-citation citation-type="">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Hirate]]></surname>
<given-names><![CDATA[Y.]]></given-names>
</name>
</person-group>
<source><![CDATA[J. Appl. Phys.]]></source>
<year>2015</year>
<volume>117</volume>
</nlm-citation>
</ref>
<ref id="B13">
<label>13</label><nlm-citation citation-type="">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Rincón]]></surname>
<given-names><![CDATA[C.]]></given-names>
</name>
<name>
<surname><![CDATA[Marcano]]></surname>
<given-names><![CDATA[G.]]></given-names>
</name>
<name>
<surname><![CDATA[Casanova]]></surname>
<given-names><![CDATA[R.]]></given-names>
</name>
<name>
<surname><![CDATA[Delgado]]></surname>
<given-names><![CDATA[G. E.]]></given-names>
</name>
<name>
<surname><![CDATA[Marín]]></surname>
<given-names><![CDATA[G.]]></given-names>
</name>
<name>
<surname><![CDATA[Sánchez-Pérez]]></surname>
<given-names><![CDATA[G.]]></given-names>
</name>
</person-group>
<source><![CDATA[Phys. Status Solidi B]]></source>
<year>2016</year>
<volume>253</volume>
</nlm-citation>
</ref>
<ref id="B14">
<label>14</label><nlm-citation citation-type="">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Marcano]]></surname>
<given-names><![CDATA[G.]]></given-names>
</name>
<name>
<surname><![CDATA[Sánchez-Pérez]]></surname>
<given-names><![CDATA[G.]]></given-names>
</name>
<name>
<surname><![CDATA[Rincón]]></surname>
<given-names><![CDATA[C.]]></given-names>
</name>
</person-group>
<source><![CDATA[Physica Status Solidi B]]></source>
<year>2017</year>
</nlm-citation>
</ref>
<ref id="B15">
<label>15</label><nlm-citation citation-type="">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Urbach]]></surname>
<given-names><![CDATA[F.]]></given-names>
</name>
</person-group>
<source><![CDATA[Phys. Rev.]]></source>
<year>1953</year>
<volume>92</volume>
</nlm-citation>
</ref>
<ref id="B16">
<label>16</label><nlm-citation citation-type="">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Kurik]]></surname>
<given-names><![CDATA[M.V.]]></given-names>
</name>
</person-group>
<source><![CDATA[Phys. Status Solidi A]]></source>
<year>1971</year>
<volume>8</volume>
<page-range>9</page-range></nlm-citation>
</ref>
<ref id="B17">
<label>17</label><nlm-citation citation-type="">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Cody]]></surname>
<given-names><![CDATA[G. D.]]></given-names>
</name>
<name>
<surname><![CDATA[Tiedje]]></surname>
<given-names><![CDATA[T.]]></given-names>
</name>
<name>
<surname><![CDATA[Abeles]]></surname>
<given-names><![CDATA[B.]]></given-names>
</name>
<name>
<surname><![CDATA[Goldstein]]></surname>
<given-names><![CDATA[Y.]]></given-names>
</name>
</person-group>
<source><![CDATA[Phys. Rev. Lett.]]></source>
<year>1981</year>
<volume>47</volume>
</nlm-citation>
</ref>
<ref id="B18">
<label>18</label><nlm-citation citation-type="">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Wasim]]></surname>
<given-names><![CDATA[S. M.]]></given-names>
</name>
</person-group>
<source><![CDATA[Phys. Rev. B]]></source>
<year>2001</year>
<volume>64</volume>
</nlm-citation>
</ref>
<ref id="B19">
<label>19</label><nlm-citation citation-type="">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Bonalde]]></surname>
<given-names><![CDATA[I.]]></given-names>
</name>
</person-group>
<source><![CDATA[Phys. Rev. B]]></source>
<year>2004</year>
<volume>69</volume>
</nlm-citation>
</ref>
<ref id="B20">
<label>20</label><nlm-citation citation-type="">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Wasim]]></surname>
<given-names><![CDATA[S. M.]]></given-names>
</name>
<name>
<surname><![CDATA[Marín]]></surname>
<given-names><![CDATA[G.]]></given-names>
</name>
<name>
<surname><![CDATA[Rincón]]></surname>
<given-names><![CDATA[C.]]></given-names>
</name>
<name>
<surname><![CDATA[Sánchez-Pérez]]></surname>
<given-names><![CDATA[G.]]></given-names>
</name>
<name>
<surname><![CDATA[Mora]]></surname>
<given-names><![CDATA[A. E.]]></given-names>
</name>
</person-group>
<source><![CDATA[J. Appl. Phys.]]></source>
<year>1998</year>
<volume>83</volume>
</nlm-citation>
</ref>
<ref id="B21">
<label>21</label><nlm-citation citation-type="">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Eom]]></surname>
<given-names><![CDATA[S. H.]]></given-names>
</name>
<name>
<surname><![CDATA[Kim]]></surname>
<given-names><![CDATA[D. J.]]></given-names>
</name>
<name>
<surname><![CDATA[Yu]]></surname>
<given-names><![CDATA[Y.-M.]]></given-names>
</name>
<name>
<surname><![CDATA[Choi]]></surname>
<given-names><![CDATA[Y. D.]]></given-names>
</name>
</person-group>
<source><![CDATA[J. Alloys Comp.]]></source>
<year>2005</year>
<volume>388</volume>
<page-range>190</page-range></nlm-citation>
</ref>
<ref id="B22">
<label>22</label><nlm-citation citation-type="">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Wasim]]></surname>
<given-names><![CDATA[S. M.]]></given-names>
</name>
<name>
<surname><![CDATA[Marín]]></surname>
<given-names><![CDATA[G.]]></given-names>
</name>
<name>
<surname><![CDATA[Rincón]]></surname>
<given-names><![CDATA[C.]]></given-names>
</name>
<name>
<surname><![CDATA[Rincón]]></surname>
<given-names><![CDATA[A.]]></given-names>
</name>
<name>
<surname><![CDATA[Essaleh]]></surname>
<given-names><![CDATA[L.]]></given-names>
</name>
</person-group>
<source><![CDATA[Superlattices Microstruct.]]></source>
<year>2015</year>
<volume>85</volume>
</nlm-citation>
</ref>
<ref id="B23">
<label>23</label><nlm-citation citation-type="">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Wasim]]></surname>
<given-names><![CDATA[S.M.]]></given-names>
</name>
<name>
<surname><![CDATA[Marín]]></surname>
<given-names><![CDATA[G.]]></given-names>
</name>
<name>
<surname><![CDATA[Rincón]]></surname>
<given-names><![CDATA[C.]]></given-names>
</name>
<name>
<surname><![CDATA[Sánchez-Pérez]]></surname>
<given-names><![CDATA[G.]]></given-names>
</name>
</person-group>
<source><![CDATA[J. Appl. Phys.]]></source>
<year>1998</year>
<volume>84</volume>
</nlm-citation>
</ref>
<ref id="B24">
<label>24</label><nlm-citation citation-type="">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Rincón]]></surname>
<given-names><![CDATA[C.]]></given-names>
</name>
</person-group>
<source><![CDATA[J. Appl. Phys.]]></source>
<year>2001</year>
<volume>90</volume>
</nlm-citation>
</ref>
<ref id="B25">
<label>25</label><nlm-citation citation-type="">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Arushanov]]></surname>
<given-names><![CDATA[E.]]></given-names>
</name>
</person-group>
<source><![CDATA[Phys. Staus Solidi A]]></source>
<year>2006</year>
<volume>203</volume>
</nlm-citation>
</ref>
<ref id="B26">
<label>26</label><nlm-citation citation-type="">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Marcano]]></surname>
<given-names><![CDATA[G.]]></given-names>
</name>
</person-group>
<source><![CDATA[Solid State Comm.]]></source>
<year>2008</year>
<volume>146</volume>
<page-range>65</page-range></nlm-citation>
</ref>
<ref id="B27">
<label>27</label><nlm-citation citation-type="">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Parthé]]></surname>
<given-names><![CDATA[E.]]></given-names>
</name>
<name>
<surname><![CDATA[Garin]]></surname>
<given-names><![CDATA[J.]]></given-names>
</name>
</person-group>
<source><![CDATA[Monatsh. Chem.]]></source>
<year>1971</year>
<volume>102</volume>
</nlm-citation>
</ref>
<ref id="B28">
<label>28</label><nlm-citation citation-type="">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Viña]]></surname>
<given-names><![CDATA[L.]]></given-names>
</name>
<name>
<surname><![CDATA[Logothetidis]]></surname>
<given-names><![CDATA[S.]]></given-names>
</name>
<name>
<surname><![CDATA[Cardona]]></surname>
<given-names><![CDATA[M.]]></given-names>
</name>
</person-group>
<source><![CDATA[Phys. Rev. B]]></source>
<year>1984</year>
</nlm-citation>
</ref>
<ref id="B29">
<label>29</label><nlm-citation citation-type="">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Piskach]]></surname>
<given-names><![CDATA[L. V.]]></given-names>
</name>
<name>
<surname><![CDATA[Parasyuk]]></surname>
<given-names><![CDATA[O. V.]]></given-names>
</name>
<name>
<surname><![CDATA[Romanyuk]]></surname>
<given-names><![CDATA[Y. E.]]></given-names>
</name>
</person-group>
<source><![CDATA[J. Alloy Compd.]]></source>
<year>2000</year>
<volume>299</volume>
<page-range>227</page-range></nlm-citation>
</ref>
<ref id="B30">
<label>30</label><nlm-citation citation-type="">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Premkumar]]></surname>
<given-names><![CDATA[D. S.]]></given-names>
</name>
<name>
<surname><![CDATA[Chetty]]></surname>
<given-names><![CDATA[R.]]></given-names>
</name>
<name>
<surname><![CDATA[Malar]]></surname>
<given-names><![CDATA[P.]]></given-names>
</name>
<name>
<surname><![CDATA[Mallik]]></surname>
<given-names><![CDATA[R. C.]]></given-names>
</name>
</person-group>
<source><![CDATA[AIP Conference Proceedings]]></source>
<year>2015</year>
<volume>1665</volume>
</nlm-citation>
</ref>
</ref-list>
</back>
</article>
