How to remove the option "Search This Site" from search box on customized Master Page in SP 2013

Hi Everyone,

I want to remove the option "This Site" from search box on Master page. I have searched this forum and found tips. I have added the

<Property Name="DropDownModeEx">ShowDD_NoContextual</Property>

in the file SearchArea under

C:\Program Files\Common Files\Microsoft Shared\web server extensions\14\TEMPLATE\FEATURES\OSearchEnhancedFeature

But it didn't work. The tips is for SP 2007. Anyone can help me to change this in Sp 2013?

Thanks.

<?xml version="1.0" encoding="utf-8" ?>
<Elements xmlns="http://schemas.microsoft.com/sharepoint/">
    <Control
        Id="SmallSearchInputBox"
        Sequence="25"
        ControlClass="Microsoft.SharePoint.Portal.WebControls.SearchBoxEx" ControlAssembly="Microsoft.Office.Server.Search, Version=14.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c">
 <Property Name="GoImageUrl">/_layouts/images/gosearch15.png</Property>
 <Property Name="GoImageUrlRTL">/_layouts/images/gosearchrtl15.png</Property>
 <Property Name="GoImageActiveUrl">/_layouts/images/gosearchhover15.png</Property>
 <Property Name="GoImageActiveUrlRTL">/_layouts/images/gosearchrtlhover15.png</Property>
        <Property Name="UseSiteDefaults">true</Property>
        <Property Name="FrameType">None</Property>
        <Property Name="ShowAdvancedSearch">false</Property>
        <Property Name="DropDownModeEx">HideScopeDD_DefaultContextual</Property>
 <Property Name="DropDownModeEx">ShowDD_NoContextual</Property>
        <Property Name="UseSiteDropDownMode">true</Property>
    </Control>   
</Elements>

This is the link I found

http://social.technet.microsoft.com/Forums/sharepoint/en-US/dc35ccf4-bc94-4827-9f16-83478c8642d1/removing-thissite-from-search-dropdown